Merge branch 'master' into mocks-and-doubles

2024-08-15 00:53:35 +00:00 · 2020-02-23 12:00:37 -07:00 · 2020-02-23 12:00:37 -07:00 · 86729c6745
commit 86729c6745
parent 1382f75030 5543c07766
70 changed files with 1799 additions and 209 deletions
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@ -15,6 +15,9 @@ before_script:
 spec:
  script:
  - crystal spec --error-on-warnings
+
+style:
+  script:
  - bin/ameba
  - crystal tool format --check

--- a/.guardian.yml
+++ b/.guardian.yml
@ -0,0 +1,5 @@
+files: ./**/*.cr
+run: time crystal spec --error-trace
+---
+files: ./shard.yml
+run: shards
--- a/shard.yml
+++ b/shard.yml
@ -1,16 +1,16 @@
 name: spectator
-version: 0.9.1
+version: 0.9.9
 description: |
  A feature-rich spec testing framework for Crystal with similarities to RSpec.

 authors:
  - Michael Miller <icy.arctic.fox@gmail.com>

-crystal: 0.31.0
+crystal: 0.33.0

 license: MIT

 development_dependencies:
  ameba:
    github: crystal-ameba/ameba
-    version: ~> 0.10
+    version: ~> 0.11.0
--- a/spec/matchers/equality_matcher_spec.cr
+++ b/spec/matchers/equality_matcher_spec.cr
@ -0,0 +1,32 @@
+require "../spec_helper"
+
+Spectator.describe "eq matcher" do
+  it "is true for equal values" do
+    expect(42).to eq(42)
+  end
+
+  it "is false for inequal values" do
+    expect(42).to_not eq(24)
+  end
+
+  it "is true for identical references" do
+    string = "foobar"
+    expect(string).to eq(string)
+  end
+
+  it "is false for different references" do
+    string1 = "foo"
+    string2 = "bar"
+    expect(string1).to_not eq(string2)
+  end
+
+  double(:fake) do
+    stub instance.==(other) { true }
+  end
+
+  it "uses the == operator" do
+    dbl = double(:fake)
+    expect(42).to eq(dbl)
+    expect(dbl).to have_received(:==).with(42).once
+  end
+end
--- a/spec/rspec/core/before_and_after_hooks_spec.cr
+++ b/spec/rspec/core/before_and_after_hooks_spec.cr
@ -0,0 +1,112 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-core/v/3-8/docs/hooks/before-and-after-hooks
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`before` and `after` hooks" do
+  context "Define `before_each` block" do
+    class Thing
+      def widgets
+        @widgets ||= [] of Symbol # Must specify array element type.
+      end
+    end
+
+    describe Thing do
+      before_each do
+        @thing = Thing.new
+      end
+
+      describe "initialize in before_each" do
+        it "has 0 widgets" do
+          widgets = @thing.as(Thing).widgets # Must cast since compile type is Thing?
+          expect(widgets.size).to eq(0)      # Use size instead of count.
+        end
+
+        it "can accept new widgets" do
+          widgets = @thing.as(Thing).widgets # Must cast since compile type is Thing?
+          widgets << :foo
+        end
+
+        it "does not share state across examples" do
+          widgets = @thing.as(Thing).widgets # Must cast since compile type is Thing?
+          expect(widgets.size).to eq(0)      # Use size instead of count.
+        end
+      end
+    end
+  end
+
+  context "Define `before_all` block in example group" do
+    class Thing
+      def widgets
+        @widgets ||= [] of Symbol # Must specify array element type.
+      end
+    end
+
+    describe Thing do
+      # Moved before_all into the same example group.
+      # Unlike Ruby, inherited class variables don't share the same value.
+      # See: https://crystal-lang.org/reference/syntax_and_semantics/class_variables.html
+      describe "initialized in before_all" do
+        @@thing : Thing?
+
+        before_all do
+          @@thing = Thing.new # Must use class variables.
+        end
+
+        it "has 0 widgets" do
+          widgets = @@thing.as(Thing).widgets # Must cast since compile type is Thing?
+          expect(widgets.size).to eq(0)       # Use size instead of count.
+        end
+
+        it "can accept new widgets" do
+          widgets = @@thing.as(Thing).widgets # Must cast since compile type is Thing?
+          widgets << :foo
+        end
+
+        it "shares state across examples" do
+          widgets = @@thing.as(Thing).widgets # Must cast since compile type is Thing?
+          expect(widgets.size).to eq(1)       # Use size instead of count.
+        end
+      end
+    end
+  end
+
+  context "Failure in `before_each` block" do
+    # TODO
+  end
+
+  context "Failure in `after_each` block" do
+    # TODO
+  end
+
+  context "Define `before` and `after` blocks in configuration" do
+    # TODO
+  end
+
+  context "`before`/`after` blocks are run in order" do
+    # Examples changed from using puts to appending to an array.
+    describe "before and after callbacks" do
+      @@order = [] of Symbol
+
+      before_all do
+        @@order << :before_all
+      end
+
+      before_each do
+        @@order << :before_each
+      end
+
+      after_each do
+        @@order << :after_each
+      end
+
+      after_all do
+        @@order << :after_all
+      end
+
+      it "gets run in order" do
+        expect(@@order).to_eventually eq(%i[before_all before_each after_each after_all])
+      end
+    end
+  end
+end
--- a/spec/rspec/core/explicit_subject_spec.cr
+++ b/spec/rspec/core/explicit_subject_spec.cr
@ -0,0 +1,140 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-core/v/3-8/docs/subject/explicit-subject
+# and modified to fit Spectator and Crystal.
+Spectator.describe "Explicit Subject" do
+  context "A `subject` can be defined and used in the top level group scope" do
+    describe Array(Int32) do # TODO: Multiple arguments to describe/context.
+      subject { [1, 2, 3] }
+
+      it "has the prescribed elements" do
+        expect(subject).to eq([1, 2, 3])
+      end
+    end
+  end
+
+  context "The `subject` define in an outer group is available to inner groups" do
+    describe Array(Int32) do
+      subject { [1, 2, 3] }
+
+      describe "has some elements" do
+        it "which are the prescribed elements" do
+          expect(subject).to eq([1, 2, 3])
+        end
+      end
+    end
+  end
+
+  context "The `subject` is memoized within an example but not across examples" do
+    describe Array(Int32) do
+      # Changed to class variable to get around compiler error/crash.
+      # Unhandled exception: Negative argument (ArgumentError)
+      @@element_list = [1, 2, 3]
+
+      subject { @@element_list.pop }
+
+      # TODO: RSpec calls the "actual" block after the "change block".
+      xit "is memoized across calls (i.e. the block is invoked once)" do
+        expect do
+          3.times { subject }
+        end.to change { @@element_list }.from([1, 2, 3]).to([1, 2])
+        expect(subject).to eq(3)
+      end
+
+      # TODO: RSpec calls the "actual" block after the "change block".
+      xit "is not memoized across examples" do
+        expect { subject }.to change { @@element_list }.from([1, 2]).to([1])
+        expect(subject).to eq(2)
+      end
+    end
+  end
+
+  context "The `subject` is available in `before` blocks" do
+    describe Array(Int32) do # TODO: Multiple arguments to describe/context.
+      subject { [] of Int32 }
+
+      before_each { subject.push(1, 2, 3) }
+
+      it "has the prescribed elements" do
+        expect(subject).to eq([1, 2, 3])
+      end
+    end
+  end
+
+  context "Helper methods can be invoked from a `subject` definition block" do
+    describe Array(Int32) do # TODO: Multiple arguments to describe/context.
+      def prepared_array
+        [1, 2, 3]
+      end
+
+      subject { prepared_array }
+
+      it "has the prescribed elements" do
+        expect(subject).to eq([1, 2, 3])
+      end
+    end
+  end
+
+  context "Use the `subject!` bang method to call the definition block before the example" do
+    describe "eager loading with subject!" do
+      subject! { element_list.push(99) }
+
+      let(:element_list) { [1, 2, 3] }
+
+      it "calls the definition block before the example" do
+        element_list.push(5)
+        expect(element_list).to eq([1, 2, 3, 99, 5])
+      end
+    end
+  end
+
+  context "Use `subject(:name)` to define a memoized helper method" do
+    # Globals not supported, using class variable instead.
+    @@count = 0
+
+    describe "named subject" do
+      subject(:global_count) { @@count += 1 }
+
+      it "is memoized across calls (i.e. the block is invoked once)" do
+        expect do
+          2.times { global_count }
+        end.not_to change { global_count }.from(1)
+      end
+
+      it "is not cached across examples" do
+        expect(global_count).to eq(2)
+      end
+
+      it "is still available using the subject method" do
+        expect(subject).to eq(3)
+      end
+
+      it "works with the one-liner syntax" do
+        is_expected.to eq(4)
+      end
+
+      it "the subject and named helpers return the same object" do
+        expect(global_count).to be(subject)
+      end
+
+      it "is set to the block return value (i.e. the global $count)" do
+        expect(global_count).to be(@@count)
+      end
+    end
+  end
+
+  context "Use `subject!(:name)` to define a helper method called before the example" do
+    describe "eager loading using a named subject!" do
+      subject!(:updated_list) { element_list.push(99) }
+
+      let(:element_list) { [1, 2, 3] }
+
+      it "calls the definition block before the example" do
+        element_list.push(5)
+        expect(element_list).to eq([1, 2, 3, 99, 5])
+        expect(updated_list).to be(element_list)
+      end
+    end
+  end
+end
--- a/spec/rspec/core/helper_methods_spec.cr
+++ b/spec/rspec/core/helper_methods_spec.cr
@ -0,0 +1,29 @@
+require "../../spec_helper"
+
+Spectator.describe "Arbitrary helper methods" do
+  context "Use a method define in the same group" do
+    describe "an example" do
+      def help
+        :available
+      end
+
+      it "has access to methods define in its group" do
+        expect(help).to be(:available)
+      end
+    end
+  end
+
+  context "Use a method defined in a parent group" do
+    describe "an example" do
+      def help
+        :available
+      end
+
+      describe "in a nested group" do
+        it "has access to methods defined in its parent group" do
+          expect(help).to be(:available)
+        end
+      end
+    end
+  end
+end
--- a/spec/rspec/core/implicit_subject_spec.cr
+++ b/spec/rspec/core/implicit_subject_spec.cr
@ -0,0 +1,43 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-core/v/3-8/docs/subject/implicitly-defined-subject
+# and modified to fit Spectator and Crystal.
+Spectator.describe "Implicitly defined subject" do
+  context "`subject` exposed in top-level group" do
+    describe Array(String) do
+      it "should be empty when first created" do
+        expect(subject).to be_empty
+      end
+    end
+  end
+
+  context "`subject` in a nested group" do
+    describe Array(String) do
+      describe "when first created" do
+        it "should  be empty" do
+          expect(subject).to be_empty
+        end
+      end
+    end
+  end
+
+  context "`subject` in a nested group with a different class (innermost wins)" do
+    class ArrayWithOneElement < Array(String)
+      def initialize(*_args)
+        super
+        unshift "first element"
+      end
+    end
+
+    describe Array(String) do
+      describe ArrayWithOneElement do
+        context "referenced as subject" do
+          it "contains one element" do
+            expect(subject).to contain("first element")
+          end
+        end
+      end
+    end
+  end
+end
--- a/spec/rspec/core/let_spec.cr
+++ b/spec/rspec/core/let_spec.cr
@ -0,0 +1,45 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-core/v/3-8/docs/helper-methods/let-and-let
+# and modified to fit Spectator and Crystal.
+Spectator.describe "Let and let!" do
+  context "Use `let` to define memoized helper method" do
+    # Globals aren't supported, use class variables instead.
+    @@count = 0
+
+    describe "let" do
+      let(:count) { @@count += 1 }
+
+      it "memoizes thte value" do
+        expect(count).to eq(1)
+        expect(count).to eq(1)
+      end
+
+      it "is not cached across examples" do
+        expect(count).to eq(2)
+      end
+    end
+  end
+
+  context "Use `let!` to define a memoized helper method that is called in a `before` hook" do
+    # Globals aren't supported, use class variables instead.
+    @@count = 0
+
+    describe "let!" do
+      # Use class variable here.
+      @@invocation_order = [] of Symbol
+
+      let!(:count) do
+        @@invocation_order << :let!
+        @@count += 1
+      end
+
+      it "calls the helper method in a before hook" do
+        @@invocation_order << :example
+        expect(@@invocation_order).to eq([:let!, :example])
+        expect(count).to eq(1)
+      end
+    end
+  end
+end
--- a/spec/rspec/core/one_liner_subject_spec.cr
+++ b/spec/rspec/core/one_liner_subject_spec.cr
@ -0,0 +1,31 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-core/v/3-8/docs/subject/one-liner-syntax
+# and modified to fit Spectator and Crystal.
+Spectator.describe "One-liner syntax" do
+  context "Implicit subject" do
+    describe Array(Int32) do
+      # Rather than:
+      # it "should be empty" do
+      #   subject.should be_empty
+      # end
+
+      it { should be_empty }
+      # or
+      it { is_expected.to be_empty }
+    end
+  end
+
+  context "Explicit subject" do
+    describe Array(Int32) do
+      describe "with 3 items" do
+        subject { [1, 2, 3] }
+
+        it { should_not be_empty }
+        # or
+        it { is_expected.not_to be_empty }
+      end
+    end
+  end
+end
--- a/spec/rspec/expectations/all_matcher_spec.cr
+++ b/spec/rspec/expectations/all_matcher_spec.cr
@ -0,0 +1,37 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/all-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`all` matcher" do
+  context "array usage" do
+    describe [1, 3, 5] do
+      it { is_expected.to all(be_odd) }
+      it { is_expected.to all(be_an(Int32)) } # Changed to Int32 to satisfy compiler.
+      it { is_expected.to all(be < 10) }
+
+      # deliberate failures
+      it_fails { is_expected.to all(be_even) }
+      it_fails { is_expected.to all(be_a(String)) }
+      it_fails { is_expected.to all(be > 2) }
+    end
+  end
+
+  context "compound matcher usage" do
+    # Changed `include` to `contain` to match our own.
+    # `include` is a keyword and can't be used as a method name in Crystal.
+
+    # TODO: Add support for compound matchers.
+    describe ["anything", "everything", "something"] do
+      xit { is_expected.to all(be_a(String)) }    # .and contain("thing") ) }
+      xit { is_expected.to all(be_a(String)) }    # .and end_with("g") ) }
+      xit { is_expected.to all(start_with("s")) } # .or contain("y") ) }
+
+      # deliberate failures
+      # TODO: Add support for compound matchers.
+      xit { is_expected.to all(contain("foo")) }  # .and contain("bar") ) }
+      xit { is_expected.to all(be_a(String)) }    # .and start_with("a") ) }
+      xit { is_expected.to all(start_with("a")) } # .or contain("z") ) }
+    end
+  end
+end
--- a/spec/rspec/expectations/be_between_matcher_spec.cr
+++ b/spec/rspec/expectations/be_between_matcher_spec.cr
@ -0,0 +1,17 @@
+require "../../spec_helper"
+
+Spectator.describe "`be_between` matcher" do
+  context "basic usage" do
+    describe 7 do
+      it { is_expected.to be_between(1, 10) }
+      it { is_expected.to be_between(0.2, 27.1) }
+      it { is_expected.not_to be_between(1.5, 4) }
+      it { is_expected.not_to be_between(8, 9) }
+
+      # boundaries check
+      it { is_expected.to be_between(0, 7) }
+      it { is_expected.to be_between(7, 10) }
+      it { is_expected.not_to (be_between(0, 7).exclusive) }
+    end
+  end
+end
--- a/spec/rspec/expectations/be_matchers_spec.cr
+++ b/spec/rspec/expectations/be_matchers_spec.cr
@ -0,0 +1,66 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/be-matchers
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`be` matchers" do
+  context "be_truthy matcher" do
+    specify { expect(true).to be_truthy }
+    specify { expect(7).to be_truthy }
+    specify { expect("foo").to be_truthy }
+    specify { expect(nil).not_to be_truthy }
+    specify { expect(false).not_to be_truthy }
+
+    # deliberate failures
+    specify_fails { expect(true).not_to be_truthy }
+    specify_fails { expect(7).not_to be_truthy }
+    specify_fails { expect("foo").not_to be_truthy }
+    specify_fails { expect(nil).to be_truthy }
+    specify_fails { expect(false).to be_truthy }
+  end
+
+  context "be_falsey matcher" do
+    specify { expect(nil).to be_falsey }
+    specify { expect(false).to be_falsey }
+    specify { expect(true).not_to be_falsey }
+    specify { expect(7).not_to be_falsey }
+    specify { expect("foo").not_to be_falsey }
+
+    # deliberate failures
+    specify_fails { expect(nil).not_to be_falsey }
+    specify_fails { expect(false).not_to be_falsey }
+    specify_fails { expect(true).to be_falsey }
+    specify_fails { expect(7).to be_falsey }
+    specify_fails { expect("foo").to be_falsey }
+  end
+
+  context "be_nil matcher" do
+    specify { expect(nil).to be_nil }
+    specify { expect(false).not_to be_nil }
+    specify { expect(true).not_to be_nil }
+    specify { expect(7).not_to be_nil }
+    specify { expect("foo").not_to be_nil }
+
+    # deliberate failures
+    specify_fails { expect(nil).not_to be_nil }
+    specify_fails { expect(false).to be_nil }
+    specify_fails { expect(true).to be_nil }
+    specify_fails { expect(7).to be_nil }
+    specify_fails { expect("foo").to be_nil }
+  end
+
+  context "be matcher" do
+    specify { expect(true).to be }
+    specify { expect(7).to be }
+    specify { expect("foo").to be }
+    specify { expect(nil).not_to be }
+    specify { expect(false).not_to be }
+
+    # deliberate failures
+    specify_fails { expect(true).not_to be }
+    specify_fails { expect(7).not_to be }
+    specify_fails { expect("foo").not_to be }
+    specify_fails { expect(nil).to be }
+    specify_fails { expect(false).to be }
+  end
+end
--- a/spec/rspec/expectations/be_within_matcher_spec.cr
+++ b/spec/rspec/expectations/be_within_matcher_spec.cr
@ -0,0 +1,24 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/be-within-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`be_within` matcher" do
+  context "basic usage" do
+    describe 27.5 do
+      it { is_expected.to be_within(0.5).of(27.9) }
+      it { is_expected.to be_within(0.5).of(28.0) }
+      it { is_expected.to be_within(0.5).of(27.1) }
+      it { is_expected.to be_within(0.5).of(27.0) }
+
+      it { is_expected.not_to be_within(0.5).of(28.1) }
+      it { is_expected.not_to be_within(0.5).of(26.9) }
+
+      # deliberate failures
+      it_fails { is_expected.not_to be_within(0.5).of(28) }
+      it_fails { is_expected.not_to be_within(0.5).of(27) }
+      it_fails { is_expected.to be_within(0.5).of(28.1) }
+      it_fails { is_expected.to be_within(0.5).of(26.9) }
+    end
+  end
+end
--- a/spec/rspec/expectations/change_matcher_spec.cr
+++ b/spec/rspec/expectations/change_matcher_spec.cr
@ -0,0 +1,47 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/change-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`change` matcher" do
+  # Modified this example type to work in Crystal.
+  module Counter
+    extend self
+
+    @@count = 0
+
+    def increment
+      @@count += 1
+    end
+
+    def count
+      @@count
+    end
+  end
+
+  context "expect change" do
+    describe "Counter#increment" do # TODO: Allow multiple arguments to context/describe.
+      it "should increment the count" do
+        expect { Counter.increment }.to change { Counter.count }.from(0).to(1)
+      end
+
+      # deliberate failure
+      it_fails "should increment the count by 2" do
+        expect { Counter.increment }.to change { Counter.count }.by(2)
+      end
+    end
+  end
+
+  context "expect no change" do
+    describe "Counter#increment" do # TODO: Allow multiple arguments to context/describe.
+    # deliberate failures
+      it_fails "should not increment the count by 1 (using not_to)" do
+        expect { Counter.increment }.not_to change { Counter.count }
+      end
+
+      it_fails "should not increment the count by 1 (using to_not)" do
+        expect { Counter.increment }.to_not change { Counter.count }
+      end
+    end
+  end
+end
--- a/spec/rspec/expectations/comparison_matchers_spec.cr
+++ b/spec/rspec/expectations/comparison_matchers_spec.cr
@ -0,0 +1,44 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/comparison-matchers
+# and modified to fit Spectator and Crystal.
+Spectator.describe "Comparison matchers" do
+  context "numeric operator matchers" do
+    describe 18 do
+      it { is_expected.to be < 20 }
+      it { is_expected.to be > 15 }
+      it { is_expected.to be <= 19 }
+      it { is_expected.to be >= 17 }
+
+      # deliberate failures
+      it_fails { is_expected.to be < 15 }
+      it_fails { is_expected.to be > 20 }
+      it_fails { is_expected.to be <= 17 }
+      it_fails { is_expected.to be >= 19 }
+      # it { is_expected.to be < 'a' } # Removed because Crystal doesn't support Int32#<(Char)
+    end
+
+    describe 'a' do
+      it { is_expected.to be < 'b' }
+
+      # deliberate failures
+      # it { is_expected.to be < 18 } # Removed because Crystal doesn't support Char#<(Int32)
+    end
+  end
+
+  context "string operator matchers" do
+    describe "Strawberry" do
+      it { is_expected.to be < "Tomato" }
+      it { is_expected.to be > "Apple" }
+      it { is_expected.to be <= "Turnip" }
+      it { is_expected.to be >= "Banana" }
+
+      # deliberate failures
+      it_fails { is_expected.to be < "Cranberry" }
+      it_fails { is_expected.to be > "Zuchini" }
+      it_fails { is_expected.to be <= "Potato" }
+      it_fails { is_expected.to be >= "Tomato" }
+    end
+  end
+end
--- a/spec/rspec/expectations/contain_exactly_matcher_spec.cr
+++ b/spec/rspec/expectations/contain_exactly_matcher_spec.cr
@ -0,0 +1,30 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/contain-exactly-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`contain_exactly` matcher" do
+  context "Array is expected to contain every value" do
+    describe [1, 2, 3] do
+      it { is_expected.to contain_exactly(1, 2, 3) }
+      it { is_expected.to contain_exactly(1, 3, 2) }
+      it { is_expected.to contain_exactly(2, 1, 3) }
+      it { is_expected.to contain_exactly(2, 3, 1) }
+      it { is_expected.to contain_exactly(3, 1, 2) }
+      it { is_expected.to contain_exactly(3, 2, 1) }
+
+      # deliberate failures
+      it_fails { is_expected.to contain_exactly(1, 2, 1) }
+    end
+  end
+
+  context "Array is not expected to contain every value" do
+    describe [1, 2, 3] do
+      it { is_expected.to_not contain_exactly(1, 2, 3, 4) }
+      it { is_expected.to_not contain_exactly(1, 2) }
+
+      # deliberate failures
+      it_fails { is_expected.to_not contain_exactly(1, 3, 2) }
+    end
+  end
+end
--- a/spec/rspec/expectations/contain_matcher_spec.cr
+++ b/spec/rspec/expectations/contain_matcher_spec.cr
@ -0,0 +1,96 @@
+require "../../spec_helper"
+
+# In Ruby, this is the `include` matcher.
+# However, `include` is a reserved keyword in Crystal.
+# So instead, it is `contain` in Spectator.
+Spectator.describe "`contain` matcher" do
+  context "array usage" do
+    describe [1, 3, 7] do
+      it { is_expected.to contain(1) }
+      it { is_expected.to contain(3) }
+      it { is_expected.to contain(7) }
+      it { is_expected.to contain(1, 7) }
+      it { is_expected.to contain(1, 3, 7) }
+
+      # Utility matcher method `a_kind_of` is not supported.
+      # it { is_expected.to contain(a_kind_of(Int)) }
+
+      # TODO: Compound matchers aren't supported.
+      # it { is_expected.to contain(be_odd.and be < 10) }
+
+      # TODO: Fix behavior and cleanup output.
+      # This syntax is allowed, but produces a wrong result and bad output.
+      xit { is_expected.to contain(be_odd) }
+      xit { is_expected.not_to contain(be_even) }
+
+      it { is_expected.not_to contain(17) }
+      it { is_expected.not_to contain(43, 100) }
+
+      # deliberate failures
+      it_fails { is_expected.to contain(4) }
+      it_fails { is_expected.to contain(be_even) }
+      it_fails { is_expected.not_to contain(1) }
+      it_fails { is_expected.not_to contain(3) }
+      it_fails { is_expected.not_to contain(7) }
+      it_fails { is_expected.not_to contain(1, 3, 7) }
+
+      # both of these should fail since it contains 1 but not 9
+      it_fails { is_expected.to contain(1, 9) }
+      it_fails { is_expected.not_to contain(1, 9) }
+    end
+  end
+
+  context "string usage" do
+    describe "a string" do
+      it { is_expected.to contain("str") }
+      it { is_expected.to contain("a", "str", "ng") }
+      it { is_expected.not_to contain("foo") }
+      it { is_expected.not_to contain("foo", "bar") }
+
+      # deliberate failures
+      it_fails { is_expected.to contain("foo") }
+      it_fails { is_expected.not_to contain("str") }
+      it_fails { is_expected.to contain("str", "foo") }
+      it_fails { is_expected.not_to contain("str", "foo") }
+    end
+  end
+
+  context "hash usage" do
+    # A hash can't be described inline here for some reason.
+    # So it is placed in the subject instead.
+    describe ":a => 7, :b => 5" do
+      subject { {:a => 7, :b => 5} }
+
+      # Hash syntax is changed here from `:a => 7` to `a: 7`.
+      # it { is_expected.to contain(:a) }
+      # it { is_expected.to contain(:b, :a) }
+
+      # TODO: This hash-like syntax isn't supported.
+      # it { is_expected.to contain(a: 7) }
+      # it { is_expected.to contain(b: 5, a: 7) }
+      # it { is_expected.not_to contain(:c) }
+      # it { is_expected.not_to contain(:c, :d) }
+      # it { is_expected.not_to contain(d: 2) }
+      # it { is_expected.not_to contain(a: 5) }
+      # it { is_expected.not_to contain(b: 7, a: 5) }
+
+      # deliberate failures
+      # it { is_expected.not_to contain(:a) }
+      # it { is_expected.not_to contain(:b, :a) }
+      # it { is_expected.not_to contain(a: 7) }
+      # it { is_expected.not_to contain(a: 7, b: 5) }
+      # it { is_expected.to contain(:c) }
+      # it { is_expected.to contain(:c, :d) }
+      # it { is_expected.to contain(d: 2) }
+      # it { is_expected.to contain(a: 5) }
+      # it { is_expected.to contain(a: 5, b: 7) }
+
+      # Mixed cases--the hash contains one but not the other.
+      # All 4 of these cases should fail.
+      # it { is_expected.to contain(:a, :d) }
+      # it { is_expected.not_to contain(:a, :d) }
+      # it { is_expected.to contain(a: 7, d: 3) }
+      # it { is_expected.not_to contain(a: 7, d: 3) }
+    end
+  end
+end
--- a/spec/rspec/expectations/cover_matcher_spec.cr
+++ b/spec/rspec/expectations/cover_matcher_spec.cr
@ -0,0 +1,29 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/cover-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`cover` matcher" do
+  context "range usage" do
+    describe (1..10) do
+      it { is_expected.to cover(4) }
+      it { is_expected.to cover(6) }
+      it { is_expected.to cover(8) }
+      it { is_expected.to cover(4, 6) }
+      it { is_expected.to cover(4, 6, 8) }
+      it { is_expected.not_to cover(11) }
+      it { is_expected.not_to cover(11, 12) }
+
+      # deliberate failures
+      it_fails { is_expected.to cover(11) }
+      it_fails { is_expected.not_to cover(4) }
+      it_fails { is_expected.not_to cover(6) }
+      it_fails { is_expected.not_to cover(8) }
+      it_fails { is_expected.not_to cover(4, 6, 8) }
+
+      # both of these should fail since it covers 5 but not 11
+      it_fails { is_expected.to cover(5, 11) }
+      it_fails { is_expected.not_to cover(5, 11) }
+    end
+  end
+end
--- a/spec/rspec/expectations/end_with_matcher_spec.cr
+++ b/spec/rspec/expectations/end_with_matcher_spec.cr
@ -0,0 +1,31 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/end-with-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`end_with` matcher" do
+  context "string usage" do
+    describe "this string" do
+      it { is_expected.to end_with "string" }
+      it { is_expected.not_to end_with "stringy" }
+
+      # deliberate failures
+      it_fails { is_expected.not_to end_with "string" }
+      it_fails { is_expected.to end_with "stringy" }
+    end
+  end
+
+  context "array usage" do
+    describe [0, 1, 2, 3, 4] do
+      it { is_expected.to end_with 4 }
+      # TODO: Add support for multiple items at the end of an array.
+      # it { is_expected.to end_with 3, 4 }
+      it { is_expected.not_to end_with 3 }
+      # it { is_expected.not_to end_with 0, 1, 2, 3, 4, 5 }
+
+      # deliberate failures
+      it_fails { is_expected.not_to end_with 4 }
+      it_fails { is_expected.to end_with 3 }
+    end
+  end
+end
--- a/spec/rspec/expectations/equality_matchers_spec.cr
+++ b/spec/rspec/expectations/equality_matchers_spec.cr
@ -0,0 +1,64 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/equality-matchers
+# and modified to fit Spectator and Crystal.
+Spectator.describe "Equality matchers" do
+  context "compare using eq (==)" do
+    describe "a string" do
+      it "is equal to another string of the same value" do
+        expect("this string").to eq("this string")
+      end
+
+      it "is not equal to another string of a different value" do
+        expect("this string").not_to eq("a different string")
+      end
+    end
+
+    describe "an integer" do
+      it "is equal to a float for the same value" do
+        expect(5).to eq(5.0)
+      end
+    end
+  end
+
+  context "compare using ==" do
+    describe "a string" do
+      it "is equal to another string of the same value" do
+        expect("this string").to be == "this string"
+      end
+
+      it "is not equal to another string of a different value" do
+        expect("this string").not_to be == "a different string"
+      end
+    end
+
+    describe "an integer" do
+      it "is equal to a float of the same value" do
+        expect(5).to be == 5.0
+      end
+    end
+  end
+
+  # There are no #eql? and #equal? methods in Crystal, so these tests are skipped.
+
+  context "compare using be (same?)" do
+    it "is equal to itself" do
+      string = "this string"
+      expect(string).to be(string)
+    end
+
+    it "is not equal to another reference of the same value" do
+      # Strings with identical contents are the same reference in Crystal.
+      # This test is modified to reflect that.
+      # expect("this string").not_to be("this string")
+      box1 = Box.new("this string")
+      box2 = Box.new("this string")
+      expect(box1).not_to be(box2)
+    end
+
+    it "is not equal to another string of a different value" do
+      expect("this string").not_to be("a different string")
+    end
+  end
+end
--- a/spec/rspec/expectations/have_attributes_matcher_spec.cr
+++ b/spec/rspec/expectations/have_attributes_matcher_spec.cr
@ -0,0 +1,36 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/have-attributes-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`have_attributes` matcher" do
+  context "basic usage" do
+    # Use `record` instead of `Struct.new`.
+    record Person, name : String, age : Int32
+
+    describe Person.new("Jim", 32) do
+      # Changed some syntax for Ruby hashes to Crystal named tuples.
+
+      # Spectator doesn't support helper matchers like `a_string_starting_with` and `a_value <`.
+      # But maybe in the future it will.
+      it { is_expected.to have_attributes(name: "Jim") }
+      # it { is_expected.to have_attributes(name: a_string_starting_with("J") ) }
+      it { is_expected.to have_attributes(age: 32) }
+      # it { is_expected.to have_attributes(age: (a_value > 30) ) }
+      it { is_expected.to have_attributes(name: "Jim", age: 32) }
+      # it { is_expected.to have_attributes(name: a_string_starting_with("J"), age: (a_value > 30) ) }
+      it { is_expected.not_to have_attributes(name: "Bob") }
+      it { is_expected.not_to have_attributes(age: 10) }
+      # it { is_expected.not_to have_attributes(age: (a_value < 30) ) }
+
+      # deliberate failures
+      it_fails { is_expected.to have_attributes(name: "Bob") }
+      it_fails { is_expected.to have_attributes(name: 10) }
+
+      # fails if any of the attributes don't match
+      it_fails { is_expected.to have_attributes(name: "Bob", age: 32) }
+      it_fails { is_expected.to have_attributes(name: "Jim", age: 10) }
+      it_fails { is_expected.to have_attributes(name: "Bob", age: 10) }
+    end
+  end
+end
--- a/spec/rspec/expectations/match_matcher_spec.cr
+++ b/spec/rspec/expectations/match_matcher_spec.cr
@ -0,0 +1,28 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/match-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`match` matcher" do
+  context "string usage" do
+    describe "a string" do
+      it { is_expected.to match(/str/) }
+      it { is_expected.not_to match(/foo/) }
+
+      # deliberate failures
+      it_fails { is_expected.not_to match(/str/) }
+      it_fails { is_expected.to match(/foo/) }
+    end
+  end
+
+  context "regular expression usage" do
+    describe /foo/ do
+      it { is_expected.to match("food") }
+      it { is_expected.not_to match("drinks") }
+
+      # deliberate failures
+      it_fails { is_expected.not_to match("food") }
+      it_fails { is_expected.to match("drinks") }
+    end
+  end
+end
--- a/spec/rspec/expectations/predicate_matchers_spec.cr
+++ b/spec/rspec/expectations/predicate_matchers_spec.cr
@ -0,0 +1,81 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/predicate-matchers
+# and modified to fit Spectator and Crystal.
+Spectator.describe "Predicate matchers" do
+  context "should be_zero (based on Int#zero?)" do
+    describe 0 do
+      it { is_expected.to be_zero }
+    end
+
+    describe 7 do
+      # deliberate failure
+      it_fails { is_expected.to be_zero }
+    end
+  end
+
+  context "should_not be_empty (based on Array#empty?)" do
+    describe [1, 2, 3] do
+      it { is_expected.not_to be_empty }
+    end
+
+    describe [] of Int32 do
+      # deliberate failure
+      it_fails { is_expected.not_to be_empty }
+    end
+  end
+
+  context "should have_key (based on Hash#has_key?)" do
+    describe Hash do
+      subject { {:foo => 7} }
+
+      it { is_expected.to have_key(:foo) }
+
+      # deliberate failure
+      it_fails { is_expected.to have_key(:bar) }
+    end
+  end
+
+  context "should_not have_all_string_keys (based on custom #has_all_string_keys? method)" do
+    class ::Hash(K, V)
+      def has_all_string_keys?
+        keys.all? { |k| String === k }
+      end
+    end
+
+    describe Hash do
+      context "with symbol keys" do
+        subject { {:foo => 7, :bar => 5} }
+
+        it { is_expected.not_to have_all_string_keys }
+      end
+
+      context "with string keys" do
+        subject { {"foo" => 7, "bar" => 5} }
+
+        # deliberate failure
+        it_fails { is_expected.not_to have_all_string_keys }
+      end
+    end
+  end
+
+  context "matcher arguments are passed on to the predicate method" do
+    struct ::Int
+      def multiple_of?(x)
+        (self % x).zero?
+      end
+    end
+
+    describe 12 do
+      it { is_expected.to be_multiple_of(3) }
+      it { is_expected.not_to be_multiple_of(7) }
+
+      # deliberate failures
+      it_fails { is_expected.not_to be_multiple_of(4) }
+      it_fails { is_expected.to be_multiple_of(5) }
+    end
+  end
+
+  # The examples using private methods cause a compilation error in Crystal, and can't be used here.
+end
--- a/spec/rspec/expectations/raise_error_matcher_spec.cr
+++ b/spec/rspec/expectations/raise_error_matcher_spec.cr
@ -0,0 +1,94 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/raise-error-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`raise_error` matcher" do
+  context "expect any error" do
+    # This example originally calls a non-existent method.
+    # That isn't allowed in Crystal.
+    # The example has been changed to just raise a runtime error.
+    describe "dividing by zero" do
+      it "raises" do
+        expect { 42 // 0 }.to raise_error
+      end
+    end
+  end
+
+  context "expect specific error" do
+    # Again, can't even compile if a method doesn't exist.
+    # So using a different exception here.
+    describe "dividing by zero" do
+      it "raises" do
+        expect { 42 // 0 }.to raise_error(DivisionByZeroError)
+      end
+    end
+  end
+
+  # The following examples are changed slightly.
+  # `raise Type.new(message)` is the syntax in Crystal,
+  # whereas it is `raise Type, message` in Ruby.
+  # Additionally, `StandardError` doesn't exist in Crystal,
+  # so `Exception` is used instead.
+  context "match message with a string" do
+    describe "matching error message with string" do
+      it "matches the error message" do
+        expect { raise Exception.new("this message exactly") }
+          .to raise_error("this message exactly")
+      end
+    end
+  end
+
+  context "match message with a regexp" do
+    describe "matching error message with regex" do
+      it "matches the error message" do
+        expect { raise Exception.new("my message") }
+          .to raise_error(/my mess/)
+      end
+    end
+  end
+
+  context "matching message with `with_message`" do
+    describe "matching error message with regex" do
+      it "matches the error message" do
+        expect { raise Exception.new("my message") }
+          .to raise_error.with_message(/my mess/)
+      end
+    end
+  end
+
+  context "match class + message with string" do
+    describe "matching error message with string" do
+      it "matches the error message" do
+        expect { raise Exception.new("this message exactly") }
+          .to raise_error(Exception, "this message exactly")
+      end
+    end
+  end
+
+  context "match class + message with regexp" do
+    describe "matching error message with regex" do
+      it "matches the error message" do
+        expect { raise Exception.new("my message") }
+          .to raise_error(Exception, /my mess/)
+      end
+    end
+  end
+
+  # TODO: Support passing a block to `raise_error` matcher.
+  # context "set expectations on error object passed to block" do
+  #   it "raises DivisionByZeroError" do
+  #     expect { 42 // 0 }.to raise_error do |error|
+  #       expect(error).to be_a(DivisionByZeroError)
+  #     end
+  #   end
+  # end
+
+  context "expect no error at all" do
+    describe "#to_s" do
+      it "does not raise" do
+        expect { 42.to_s }.not_to raise_error
+      end
+    end
+  end
+end
--- a/spec/rspec/expectations/respond_to_matcher_spec.cr
+++ b/spec/rspec/expectations/respond_to_matcher_spec.cr
@ -0,0 +1,28 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/respond-to-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`respond_to` matcher" do
+  context "basic usage" do
+    describe "a string" do
+      it { is_expected.to respond_to(:size) } # It's size in Crystal, not length.
+      it { is_expected.to respond_to(:hash, :class, :to_s) }
+      it { is_expected.not_to respond_to(:to_model) }
+      it { is_expected.not_to respond_to(:compact, :flatten) }
+
+      # deliberate failures
+      it_fails { is_expected.to respond_to(:to_model) }
+      it_fails { is_expected.to respond_to(:compact, :flatten) }
+      it_fails { is_expected.not_to respond_to(:size) }
+      it_fails { is_expected.not_to respond_to(:hash, :class, :to_s) }
+
+      # mixed examples--String responds to :length but not :flatten
+      # both specs should fail
+      it_fails { is_expected.to respond_to(:size, :flatten) }
+      it_fails { is_expected.not_to respond_to(:size, :flatten) }
+    end
+  end
+
+  # Spectator doesn't support argument matching with respond_to.
+end
--- a/spec/rspec/expectations/start_with_matcher_spec.cr
+++ b/spec/rspec/expectations/start_with_matcher_spec.cr
@ -0,0 +1,31 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/start-with-matcher
+# and modified to fit Spectator and Crystal.
+Spectator.describe "`start_with` matcher" do
+  context "with a string" do
+    describe "this string" do
+      it { is_expected.to start_with "this" }
+      it { is_expected.not_to start_with "that" }
+
+      # deliberate failures
+      it_fails { is_expected.not_to start_with "this" }
+      it_fails { is_expected.to start_with "that" }
+    end
+  end
+
+  context "with an array" do
+    describe [0, 1, 2, 3, 4] do
+      it { is_expected.to start_with 0 }
+      # TODO: Add support for multiple items at the beginning of an array.
+      # it { is_expected.to start_with(0, 1) }
+      it { is_expected.not_to start_with(2) }
+      # it { is_expected.not_to start_with(0, 1, 2, 3, 4, 5) }
+
+      # deliberate failures
+      it_fails { is_expected.not_to start_with 0 }
+      it_fails { is_expected.to start_with 3 }
+    end
+  end
+end
--- a/spec/rspec/expectations/type_matchers_spec.cr
+++ b/spec/rspec/expectations/type_matchers_spec.cr
@ -0,0 +1,100 @@
+require "../../spec_helper"
+
+# Examples taken from:
+# https://relishapp.com/rspec/rspec-expectations/v/3-8/docs/built-in-matchers/type-matchers
+# and modified to fit Spectator and Crystal.
+Spectator.describe "Type matchers" do
+  context "be_(a_)kind_of matcher" do
+    # The docs use Float as an example.
+    # This doesn't work with the Crystal compiler,
+    # so a custom hierarchy is used instead.
+    # "Error: can't use Number as generic type argument yet, use a more specific type"
+
+    module MyModule; end
+
+    class Base; end
+
+    class Derived < Base
+      include MyModule
+    end
+
+    describe Derived do
+      # the actual class
+      it { is_expected.to be_kind_of(Derived) }
+      it { is_expected.to be_a_kind_of(Derived) }
+      it { is_expected.to be_a(Derived) }
+
+      # the superclass
+      it { is_expected.to be_kind_of(Base) }
+      it { is_expected.to be_a_kind_of(Base) }
+      it { is_expected.to be_an(Base) }
+
+      # an included module
+      it { is_expected.to be_kind_of(MyModule) }
+      it { is_expected.to be_a_kind_of(MyModule) }
+      it { is_expected.to be_a(MyModule) }
+
+      # negative passing case
+      it { is_expected.not_to be_kind_of(String) }
+      it { is_expected.not_to be_a_kind_of(String) }
+      it { is_expected.not_to be_a(String) }
+
+      # deliberate failures
+      it_fails { is_expected.not_to be_kind_of(Derived) }
+      it_fails { is_expected.not_to be_a_kind_of(Derived) }
+      it_fails { is_expected.not_to be_a(Derived) }
+      it_fails { is_expected.not_to be_kind_of(Base) }
+      it_fails { is_expected.not_to be_a_kind_of(Base) }
+      it_fails { is_expected.not_to be_an(Base) }
+      it_fails { is_expected.not_to be_kind_of(MyModule) }
+      it_fails { is_expected.not_to be_a_kind_of(MyModule) }
+      it_fails { is_expected.not_to be_a(MyModule) }
+      it_fails { is_expected.to be_kind_of(String) }
+      it_fails { is_expected.to be_a_kind_of(String) }
+      it_fails { is_expected.to be_a(String) }
+    end
+
+    context "be_(an_)instance_of matcher" do
+      # The docs use Float as an example.
+      # This doesn't work with the Crystal compiler,
+      # so a custom hierarchy is used instead.
+      # "Error: can't use Number as generic type argument yet, use a more specific type"
+
+      module MyModule; end
+
+      class Base; end
+
+      class Derived < Base
+        include MyModule
+      end
+
+      describe Derived do
+        # the actual class
+        it { is_expected.to be_instance_of(Derived) }
+        it { is_expected.to be_an_instance_of(Derived) }
+
+        # the superclass
+        it { is_expected.not_to be_instance_of(Base) }
+        it { is_expected.not_to be_an_instance_of(Base) }
+
+        # an included module
+        it { is_expected.not_to be_instance_of(MyModule) }
+        it { is_expected.not_to be_an_instance_of(MyModule) }
+
+        # another class with no relation to the subject's hierarchy
+        it { is_expected.not_to be_instance_of(String) }
+        it { is_expected.not_to be_an_instance_of(String) }
+
+        # deliberate failures
+        it_fails { is_expected.not_to be_instance_of(Derived) }
+        it_fails { is_expected.not_to be_an_instance_of(Derived) }
+        it_fails { is_expected.to be_instance_of(Base) }
+        it_fails { is_expected.to be_an_instance_of(Base) }
+        it_fails { is_expected.to be_instance_of(MyModule) }
+        it_fails { is_expected.to be_an_instance_of(MyModule) }
+        it_fails { is_expected.to be_instance_of(String) }
+        it_fails { is_expected.to be_an_instance_of(String) }
+      end
+    end
+  end
+end
--- a/spec/spec_helper.cr
+++ b/spec/spec_helper.cr
@ -1,4 +1,13 @@
 require "../src/spectator"

-# Prevent Spectator from trying to run tests on its own.
-Spectator.autorun = false
+macro it_fails(description = nil, &block)
+  it {{description}} do
+    expect do
+      {{block.body}}
+    end.to raise_error(Spectator::ExampleFailed)
+  end
+end
+
+macro specify_fails(description = nil, &block)
+  it_fails {{description}} {{block}}
+end
--- a/spec/subject_spec.cr
+++ b/spec/subject_spec.cr
@ -0,0 +1,23 @@
+require "./spec_helper"
+
+class Base; end
+
+module SomeModule; end
+
+Spectator.describe "Subject" do
+  subject { Base.new }
+
+  context "nested" do
+    it "inherits the parent explicit subject" do
+      expect(subject).to be_a(Base)
+    end
+  end
+
+  context "module" do
+    describe SomeModule do
+      it "sets the implicit subject to the module" do
+        expect(subject).to be(SomeModule)
+      end
+    end
+  end
+end
--- a/src/spectator.cr
+++ b/src/spectator.cr
@ -6,7 +6,7 @@ module Spectator
  extend self

  # Current version of the Spectator library.
-  VERSION = "0.9.1"
+  VERSION = "0.9.9"

  # Top-level describe method.
  # All specs in a file must be wrapped in this call.
--- a/src/spectator/dsl/assertions.cr
+++ b/src/spectator/dsl/assertions.cr
@ -184,6 +184,22 @@ module Spectator
      is_expected.to_not eq({{expected}})
    end

+    macro should(matcher)
+      is_expected.to({{matcher}})
+    end
+
+    macro should_not(matcher)
+      is_expected.to_not({{matcher}})
+    end
+
+    macro should_eventually(matcher)
+      is_expected.to_eventually({{matcher}})
+    end
+
+    macro should_never(matcher)
+      is_expected.to_never({{matcher}})
+    end
+
    # Immediately fail the current test.
    # A reason can be passed,
    # which is reported in the output.
--- a/src/spectator/dsl/examples.cr
+++ b/src/spectator/dsl/examples.cr
@ -3,7 +3,7 @@ require "../spec_builder"

 module Spectator
  module DSL
-    macro it(description, _source_file = __FILE__, _source_line = __LINE__, &block)
+    macro it(description = nil, _source_file = __FILE__, _source_line = __LINE__, &block)
      {% if block.is_a?(Nop) %}
        {% if description.is_a?(Call) %}
          def %run
@ -20,17 +20,17 @@ module Spectator

      %source = ::Spectator::Source.new({{_source_file}}, {{_source_line}})
      ::Spectator::SpecBuilder.add_example(
-        {{description.is_a?(StringLiteral) ? description : description.stringify}},
+        {{description.is_a?(StringLiteral) || description.is_a?(NilLiteral) ? description : description.stringify}},
        %source,
        {{@type.name}}
      ) { |test| test.as({{@type.name}}).%run }
    end

-    macro specify(description, &block)
+    macro specify(description = nil, &block)
      it({{description}}) {{block}}
    end

-    macro pending(description, _source_file = __FILE__, _source_line = __LINE__, &block)
+    macro pending(description = nil, _source_file = __FILE__, _source_line = __LINE__, &block)
      {% if block.is_a?(Nop) %}
        {% if description.is_a?(Call) %}
          def %run
@ -47,17 +47,17 @@ module Spectator

      %source = ::Spectator::Source.new({{_source_file}}, {{_source_line}})
      ::Spectator::SpecBuilder.add_pending_example(
-        {{description.is_a?(StringLiteral) ? description : description.stringify}},
+        {{description.is_a?(StringLiteral) || description.is_a?(NilLiteral) ? description : description.stringify}},
        %source,
        {{@type.name}}
      ) { |test| test.as({{@type.name}}).%run }
    end

-    macro skip(description, &block)
+    macro skip(description = nil, &block)
      pending({{description}}) {{block}}
    end

-    macro xit(description, &block)
+    macro xit(description = nil, &block)
      pending({{description}}) {{block}}
    end
  end
--- a/src/spectator/dsl/groups.cr
+++ b/src/spectator/dsl/groups.cr
@ -19,13 +19,21 @@ module Spectator
        %source = ::Spectator::Source.new({{_source_file}}, {{_source_line}})
        ::Spectator::SpecBuilder.start_group({{description}}, %source)

-        {% if what.is_a?(Path) || what.is_a?(Generic) %}
+        {% if (what.is_a?(Path) || what.is_a?(Generic)) && (described_type = what.resolve?) %}
          macro described_class
-            {{what}}
+            {{described_type.name}}
          end

-          def subject(*args)
-            described_class.new(*args)
+          subject do
+            {% if described_type < Reference || described_type < Value %}
+              described_class.new
+            {% else %}
+              described_class
+            {% end %}
+          end
+        {% else %}
+          def _spectator_implicit_subject(*args)
+            {{what}}
          end
        {% end %}

--- a/src/spectator/dsl/matchers.cr
+++ b/src/spectator/dsl/matchers.cr
@ -94,6 +94,60 @@ module Spectator
      be_a({{expected}})
    end

+    # Indicates that some value should be of a specified type.
+    # The `Object#is_a?` method is used for this check.
+    # A type name or type union should be used for *expected*.
+    # This method is identical to `#be_a`,
+    # and exists just to improve grammar.
+    #
+    # Examples:
+    # ```
+    # expect(123).to be_kind_of(Int)
+    # ```
+    macro be_kind_of(expected)
+      be_a({{expected}})
+    end
+
+    # Indicates that some value should be of a specified type.
+    # The `Object#is_a?` method is used for this check.
+    # A type name or type union should be used for *expected*.
+    # This method is identical to `#be_a`,
+    # and exists just to improve grammar.
+    #
+    # Examples:
+    # ```
+    # expect(123).to be_a_kind_of(Int)
+    # ```
+    macro be_a_kind_of(expected)
+      be_a({{expected}})
+    end
+
+    # Indicates that some value should be of a specified type.
+    # The value's runtime class is checked.
+    # A type name or type union should be used for *expected*.
+    #
+    # Examples:
+    # ```
+    # expect(123).to be_instance_of(Int32)
+    # ```
+    macro be_instance_of(expected)
+      ::Spectator::Matchers::InstanceMatcher({{expected}}).new
+    end
+
+    # Indicates that some value should be of a specified type.
+    # The value's runtime class is checked.
+    # A type name or type union should be used for *expected*.
+    # This method is identical to `#be_an_instance_of`,
+    # and exists just to improve grammar.
+    #
+    # Examples:
+    # ```
+    # expect(123).to be_an_instance_of(Int32)
+    # ```
+    macro be_an_instance_of(expected)
+      be_instance_of({{expected}})
+    end
+
    # Indicates that some value should respond to a method call.
    # One or more method names can be provided.
    #
@ -288,10 +342,10 @@ module Spectator
    # expect(100).to be_between(97, 101).exclusive # 97, 98, 99, or 100 (not 101)
    # ```
    macro be_between(min, max)
-      %range = Range.new({{min}}, {{max}}))
+      %range = Range.new({{min}}, {{max}})
      %label = [{{min.stringify}}, {{max.stringify}}].join(" to ")
      %test_value = ::Spectator::TestValue.new(%range, %label)
-      :Spectator::Matchers::RangeMatcher.new(%test_value)
+      ::Spectator::Matchers::RangeMatcher.new(%test_value)
    end

    # Indicates that some value should be within a delta of an expected value.
@ -400,6 +454,27 @@ module Spectator
      ::Spectator::Matchers::ContainMatcher.new(%test_value)
    end

+    # Indicates that some range (or collection) should contain another value.
+    # This is typically used on a `Range` (although any `Enumerable` works).
+    # The `includes?` method is used.
+    #
+    # Examples:
+    # ```
+    # expect(1..10).to contain(5)
+    # expect((1..)).to contain(100)
+    # expect(..100).to contain(50)
+    # ```
+    #
+    # Additionally, multiple arguments can be specified.
+    # ```
+    # expect(1..10).to contain(2, 3)
+    # expect(..100).to contain(0, 50)
+    # ```
+    macro cover(*expected)
+      %test_value = ::Spectator::TestValue.new({{expected}}, {{expected.splat.stringify}})
+      ::Spectator::Matchers::ContainMatcher.new(%test_value)
+    end
+
    # Indicates that some value or set should contain another value.
    # This is similar to `#contain`, but uses a different method for matching.
    # Typically a `String` or `Array` (any `Enumerable` works) is checked against.
@ -466,22 +541,23 @@ module Spectator
      have_value({{expected}})
    end

-    # Indicates that some set should contain some values in exact order.
+    # Indicates that some set should contain some values in any order.
    #
    # Example:
    # ```
-    # expect([1, 2, 3]).to contain_exactly(1, 2, 3)
+    # expect([1, 2, 3]).to contain_exactly(3, 2, 1)
    # ```
    macro contain_exactly(*expected)
      %test_value = ::Spectator::TestValue.new({{expected}}, {{expected.stringify}})
      ::Spectator::Matchers::ArrayMatcher.new(%test_value)
    end

-    # Indicates that some set should contain the same values in exact order as another set.
+    # Indicates that some set should contain the same values in any order as another set.
+    # This is the same as `#contain_exactly`, but takes an array as an argument.
    #
    # Example:
    # ```
-    # expect([1, 2, 3]).to match_array([1, 2, 3])
+    # expect([1, 2, 3]).to match_array([3, 2, 1])
    # ```
    macro match_array(expected)
      %test_value = ::Spectator::TestValue.new({{expected}}, {{expected.stringify}})
@ -716,8 +792,8 @@ module Spectator
        {% raise "Undefined local variable or method '#{call}'" %}
      {% end %}

-      descriptor = { {{method_name}}: Tuple.new({{call.args.splat}}) }
-      label = String::Builder.new({{method_name.stringify}})
+      descriptor = { {{method_name}}: ::Tuple.new({{call.args.splat}}) }
+      label = ::String::Builder.new({{method_name.stringify}})
      {% unless call.args.empty? %}
        label << '('
        {% for arg, index in call.args %}
--- a/src/spectator/dsl/values.cr
+++ b/src/spectator/dsl/values.cr
@ -19,11 +19,18 @@ module Spectator
    end

    macro let!(name, &block)
-      # TODO: Doesn't work with late-defined values (let).
-      @%value = {{yield}}
+      @%wrapper : ::Spectator::ValueWrapper?
+
+      def %wrapper
+        {{block.body}}
+      end
+
+      before_each do
+        @%wrapper = ::Spectator::TypedValueWrapper.new(%wrapper)
+      end

      def {{name.id}}
-        @%value
+        @%wrapper.as(::Spectator::TypedValueWrapper(typeof(%wrapper))).value
      end
    end

--- a/src/spectator/example.cr
+++ b/src/spectator/example.cr
@ -6,6 +6,9 @@ module Spectator
  # Concrete types must implement the `#run_impl` method.
  abstract class Example < ExampleComponent
    @finished = false
+    @description : String? = nil
+
+    protected setter description

    # Indicates whether the example has already been run.
    def finished? : Bool
@ -24,10 +27,12 @@ module Spectator
    end

    def description : String | Symbol
-      @test_wrapper.description
+      @description || @test_wrapper.description
    end

    def symbolic? : Bool
+      return false unless @test_wrapper.description?
+
      description = @test_wrapper.description
      description.starts_with?('#') || description.starts_with?('.')
    end
--- a/src/spectator/expectations/expectation.cr
+++ b/src/spectator/expectations/expectation.cr
@ -44,6 +44,10 @@ module Spectator::Expectations
      values?.not_nil!
    end

+    def description
+      @match_data.description
+    end
+
    # Creates the JSON representation of the expectation.
    def to_json(json : ::JSON::Builder)
      json.object do
--- a/src/spectator/harness.cr
+++ b/src/spectator/harness.cr
@ -46,6 +46,7 @@ module Spectator
    # Reports the outcome of an expectation.
    # An exception will be raised when a failing result is given.
    def report_expectation(expectation : Expectations::Expectation) : Nil
+      @example.description = expectation.description unless @example.test_wrapper.description?
      @reporter.report(expectation)
    end

--- a/src/spectator/matchers/all_matcher.cr
+++ b/src/spectator/matchers/all_matcher.cr
@ -26,7 +26,7 @@ module Spectator::Matchers
        match_data = matcher.match(element)
        break match_data unless match_data.matched?
      end
-      found || SuccessfulMatchData.new
+      found || SuccessfulMatchData.new(description)
    end

    # Negated matching for this matcher is not supported.
--- a/src/spectator/matchers/array_matcher.cr
+++ b/src/spectator/matchers/array_matcher.cr
@ -5,7 +5,7 @@ require "./unordered_array_matcher"

 module Spectator::Matchers
  # Matcher for checking that the contents of one array (or similar type)
-  # has the exact same contents as another and in the same order.
+  # has the exact same contents as another but may be in any order.
  struct ArrayMatcher(ExpectedType) < Matcher
    # Expected value and label.
    private getter expected
@ -25,15 +25,19 @@ module Spectator::Matchers
    def match(actual : TestExpression(T)) : MatchData forall T
      actual_elements = actual.value.to_a
      expected_elements = expected.value.to_a
-      index = compare_arrays(expected_elements, actual_elements)
+      missing, extra = compare_arrays(expected_elements, actual_elements)

-      case index
-      when Int # Content differs.
-        failed_content_mismatch(expected_elements, actual_elements, index, actual.label)
-      when true # Contents are identical.
-        SuccessfulMatchData.new
-      else # Size differs.
-        failed_size_mismatch(expected_elements, actual_elements, actual.label)
+      if missing.empty? && extra.empty?
+        # Contents are identical.
+        SuccessfulMatchData.new(description)
+      else
+        # Content differs.
+        FailedMatchData.new(description, "#{actual.label} does not contain exactly #{expected.label}",
+          expected: expected_elements.inspect,
+          actual: actual_elements.inspect,
+          missing: missing.empty? ? "None" : missing.inspect,
+          extra: extra.empty? ? "None" : extra.inspect
+        )
      end
    end

@ -42,14 +46,17 @@ module Spectator::Matchers
    def negated_match(actual : TestExpression(T)) : MatchData forall T
      actual_elements = actual.value.to_a
      expected_elements = expected.value.to_a
+      missing, extra = compare_arrays(expected_elements, actual_elements)

-      case compare_arrays(expected_elements, actual_elements)
-      when Int # Contents differ.
-        SuccessfulMatchData.new
-      when true # Contents are identical.
-        failed_content_identical(expected_elements, actual_elements, actual.label)
-      else # Size differs.
-        SuccessfulMatchData.new
+      if missing.empty? && extra.empty?
+        # Contents are identical.
+        FailedMatchData.new(description, "#{actual.label} contains exactly #{expected.label}",
+          expected: "Not #{expected_elements.inspect}",
+          actual: actual_elements.inspect
+        )
+      else
+        # Content differs.
+        SuccessfulMatchData.new(description)
      end
    end

@ -65,49 +72,41 @@ module Spectator::Matchers
      UnorderedArrayMatcher.new(expected)
    end

-    # Compares two arrays to determine whether they contain the same elements, and in the same order.
-    # If the arrays are the same, then `true` is returned.
-    # If they are different, `false` or an integer is returned.
-    # `false` is returned when the sizes of the arrays don't match.
-    # An integer is returned, that is the index of the mismatched elements in the arrays.
+    # Compares two arrays to determine whether they contain the same elements, but in any order.
+    # A tuple of two arrays is returned.
+    # The first array is the missing elements (present in expected, missing in actual).
+    # The second array array is the extra elements (not present in expected, present in actual).
    private def compare_arrays(expected_elements, actual_elements)
-      if expected_elements.size == actual_elements.size
-        index = 0
-        expected_elements.zip(actual_elements) do |expected_element, actual_element|
-          return index unless expected_element == actual_element
-          index += 1
+      # Produce hashes where the array elements are the keys, and the values are the number of occurances.
+      expected_hash = expected_elements.group_by(&.itself).map { |k, v| {k, v.size} }.to_h
+      actual_hash = actual_elements.group_by(&.itself).map { |k, v| {k, v.size} }.to_h
+
+      {
+        hash_count_difference(expected_hash, actual_hash),
+        hash_count_difference(actual_hash, expected_hash),
+      }
    end
-        true
+
+    # Expects two hashes, with values as counts for keys.
+    # Produces an array of differences with elements repeated if needed.
+    private def hash_count_difference(first, second)
+      # Subtract the number of occurances from the other array.
+      # A duplicate hash is used here because the original can't be modified,
+      # since it there's a two-way comparison.
+      #
+      # Then reject elements that have zero (or less) occurances.
+      # Lastly, expand to the correct number of elements.
+      first.map do |element, count|
+        if second_count = second[element]?
+          {element, count - second_count}
        else
-        false
+          {element, count}
        end
-    end
-
-    # Produces match data for a failure when the array sizes differ.
-    private def failed_size_mismatch(expected_elements, actual_elements, actual_label)
-      FailedMatchData.new("#{actual_label} does not contain exactly #{expected.label} (size mismatch)",
-        expected: expected_elements.inspect,
-        actual: actual_elements.inspect,
-        "expected size": expected_elements.size.to_s,
-        "actual size": actual_elements.size.to_s
-      )
-    end
-
-    # Produces match data for a failure when the array content is mismatched.
-    private def failed_content_mismatch(expected_elements, actual_elements, index, actual_label)
-      FailedMatchData.new("#{actual_label} does not contain exactly #{expected.label} (element mismatch)",
-        expected: expected_elements[index].inspect,
-        actual: actual_elements[index].inspect,
-        index: index.to_s
-      )
-    end
-
-    # Produces match data for a failure when the arrays are identical, but they shouldn't be (negation).
-    private def failed_content_identical(expected_elements, actual_elements, actual_label)
-      FailedMatchData.new("#{actual_label} contains exactly #{expected.label}",
-        expected: "Not #{expected_elements.inspect}",
-        actual: actual_elements.inspect
-      )
+      end.reject do |(_, count)|
+        count <= 0
+      end.map do |(element, count)|
+        Array.new(count, element)
+      end.flatten
    end
  end
 end
--- a/src/spectator/matchers/attributes_matcher.cr
+++ b/src/spectator/matchers/attributes_matcher.cr
@ -28,9 +28,9 @@ module Spectator::Matchers
    def match(actual : TestExpression(T)) : MatchData forall T
      snapshot = snapshot_values(actual.value)
      if match?(snapshot)
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual.label} does not have attributes #{expected.label}", **values(snapshot))
+        FailedMatchData.new(description, "#{actual.label} does not have attributes #{expected.label}", **values(snapshot))
      end
    end

@ -39,9 +39,9 @@ module Spectator::Matchers
    def negated_match(actual : TestExpression(T)) : MatchData forall T
      snapshot = snapshot_values(actual.value)
      if match?(snapshot)
-        FailedMatchData.new("#{actual.label} has attributes #{expected.label}", **negated_values(snapshot))
+        FailedMatchData.new(description, "#{actual.label} has attributes #{expected.label}", **negated_values(snapshot))
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end

--- a/src/spectator/matchers/case_matcher.cr
+++ b/src/spectator/matchers/case_matcher.cr
@ -16,6 +16,12 @@ module Spectator::Matchers
      expected.value === actual.value
    end

+    # Overload that takes a regex so that the operands are flipped.
+    # This mimics RSpec's behavior.
+    private def match?(actual : TestExpression(Regex)) : Bool forall T
+      actual.value === expected.value
+    end
+
    # Message displayed when the matcher isn't satisifed.
    #
    # This is only called when `#match?` returns false.
--- a/src/spectator/matchers/change_exact_matcher.cr
+++ b/src/spectator/matchers/change_exact_matcher.cr
@ -30,21 +30,21 @@ module Spectator::Matchers
      before, after = change(actual)
      if expected_before == before
        if before == after
-          FailedMatchData.new("#{actual.label} did not change #{expression.label}",
+          FailedMatchData.new(description, "#{actual.label} did not change #{expression.label}",
            before: before.inspect,
            after: after.inspect
          )
        elsif expected_after == after
-          SuccessfulMatchData.new
+          SuccessfulMatchData.new(description)
        else
-          FailedMatchData.new("#{actual.label} did not change #{expression.label} to #{expected_after.inspect}",
+          FailedMatchData.new(description, "#{actual.label} did not change #{expression.label} to #{expected_after.inspect}",
            before: before.inspect,
            after: after.inspect,
            expected: expected_after.inspect
          )
        end
      else
-        FailedMatchData.new("#{expression.label} was not initially #{expected_before.inspect}",
+        FailedMatchData.new(description, "#{expression.label} was not initially #{expected_before.inspect}",
          expected: expected_before.inspect,
          actual: before.inspect,
        )
@ -57,15 +57,15 @@ module Spectator::Matchers
      before, after = change(actual)
      if expected_before == before
        if expected_after == after
-          FailedMatchData.new("#{actual.label} changed #{expression.label} from #{expected_before.inspect} to #{expected_after.inspect}",
+          FailedMatchData.new(description, "#{actual.label} changed #{expression.label} from #{expected_before.inspect} to #{expected_after.inspect}",
            before: before.inspect,
            after: after.inspect
          )
        else
-          SuccessfulMatchData.new
+          SuccessfulMatchData.new(description)
        end
      else
-        FailedMatchData.new("#{expression.label} was not initially #{expected_before.inspect}",
+        FailedMatchData.new(description, "#{expression.label} was not initially #{expected_before.inspect}",
          expected: expected_before.inspect,
          actual: before.inspect,
        )
--- a/src/spectator/matchers/change_from_matcher.cr
+++ b/src/spectator/matchers/change_from_matcher.cr
@ -27,18 +27,18 @@ module Spectator::Matchers
    def match(actual : TestExpression(T)) : MatchData forall T
      before, after = change(actual)
      if expected != before
-        FailedMatchData.new("#{expression.label} was not initially #{expected}",
+        FailedMatchData.new(description, "#{expression.label} was not initially #{expected}",
          expected: expected.inspect,
          actual: before.inspect,
        )
      elsif before == after
-        FailedMatchData.new("#{actual.label} did not change #{expression.label} from #{expected}",
+        FailedMatchData.new(description, "#{actual.label} did not change #{expression.label} from #{expected}",
          before: before.inspect,
          after: after.inspect,
          expected: "Not #{expected.inspect}"
        )
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end

@ -47,14 +47,14 @@ module Spectator::Matchers
    def negated_match(actual : TestExpression(T)) : MatchData forall T
      before, after = change(actual)
      if expected != before
-        FailedMatchData.new("#{expression.label} was not initially #{expected}",
+        FailedMatchData.new(description, "#{expression.label} was not initially #{expected}",
          expected: expected.inspect,
          actual: before.inspect
        )
      elsif before == after
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual.label} changed #{expression.label} from #{expected}",
+        FailedMatchData.new(description, "#{actual.label} changed #{expression.label} from #{expected}",
          before: before.inspect,
          after: after.inspect,
          expected: expected.inspect
--- a/src/spectator/matchers/change_matcher.cr
+++ b/src/spectator/matchers/change_matcher.cr
@ -25,12 +25,12 @@ module Spectator::Matchers
    def match(actual : TestExpression(T)) : MatchData forall T
      before, after = change(actual)
      if before == after
-        FailedMatchData.new("#{actual.label} did not change #{expression.label}",
+        FailedMatchData.new(description, "#{actual.label} did not change #{expression.label}",
          before: before.inspect,
          after: after.inspect
        )
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end

@ -39,9 +39,9 @@ module Spectator::Matchers
    def negated_match(actual : TestExpression(T)) : MatchData forall T
      before, after = change(actual)
      if before == after
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual.label} changed #{expression.label}",
+        FailedMatchData.new(description, "#{actual.label} changed #{expression.label}",
          before: before.inspect,
          after: after.inspect
        )
--- a/src/spectator/matchers/change_relative_matcher.cr
+++ b/src/spectator/matchers/change_relative_matcher.cr
@ -25,14 +25,14 @@ module Spectator::Matchers
    def match(actual : TestExpression(T)) : MatchData forall T
      before, after = change(actual)
      if before == after
-        FailedMatchData.new("#{actual.label} did not change #{expression.label}",
+        FailedMatchData.new(description, "#{actual.label} did not change #{expression.label}",
          before: before.inspect,
          after: after.inspect
        )
      elsif @evaluator.call(before, after)
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual.label} did not change #{expression.label} #{@relativity}",
+        FailedMatchData.new(description, "#{actual.label} did not change #{expression.label} #{@relativity}",
          before: before.inspect,
          after: after.inspect
        )
--- a/src/spectator/matchers/change_to_matcher.cr
+++ b/src/spectator/matchers/change_to_matcher.cr
@ -27,15 +27,15 @@ module Spectator::Matchers
    def match(actual : TestExpression(T)) : MatchData forall T
      before, after = change(actual)
      if before == after
-        FailedMatchData.new("#{actual.label} did not change #{expression.label}",
+        FailedMatchData.new(description, "#{actual.label} did not change #{expression.label}",
          before: before.inspect,
          after: after.inspect,
          expected: expected.inspect
        )
      elsif expected == after
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual.label} did not change #{expression.label} to #{expected}",
+        FailedMatchData.new(description, "#{actual.label} did not change #{expression.label} to #{expected}",
          before: before.inspect,
          after: after.inspect,
          expected: expected.inspect
--- a/src/spectator/matchers/contain_matcher.cr
+++ b/src/spectator/matchers/contain_matcher.cr
@ -18,6 +18,13 @@ module Spectator::Matchers
      end
    end

+    # If the expectation is negated, then this method is called instead of `#match?`.
+    private def does_not_match?(actual : TestExpression(T)) : Bool forall T
+      !expected.value.any? do |item|
+        actual.value.includes?(item)
+      end
+    end
+
    # Message displayed when the matcher isn't satisifed.
    #
    # This is only called when `#match?` returns false.
@ -25,7 +32,7 @@ module Spectator::Matchers
    # The message should typically only contain the test expression labels.
    # Actual values should be returned by `#values`.
    private def failure_message(actual) : String
-      "#{actual.label} does not match #{expected.label}"
+      "#{actual.label} does not contain #{expected.label}"
    end

    # Message displayed when the matcher isn't satisifed and is negated.
--- a/src/spectator/matchers/end_with_matcher.cr
+++ b/src/spectator/matchers/end_with_matcher.cr
@ -23,7 +23,8 @@ module Spectator::Matchers

    # Actually performs the test against the expression.
    def match(actual : TestExpression(T)) : MatchData forall T
-      if (value = actual.value).responds_to?(:ends_with?)
+      value = actual.value
+      if value.is_a?(String) || value.responds_to?(:ends_with?)
        match_ends_with(value, actual.label)
      else
        match_last(value, actual.label)
@ -33,10 +34,11 @@ module Spectator::Matchers
    # Performs the test against the expression, but inverted.
    # A successful match with `#match` should normally fail for this method, and vice-versa.
    def negated_match(actual : TestExpression(T)) : MatchData forall T
-      if actual.value.responds_to?(:ends_with?)
-        negated_match_ends_with(actual)
+      value = actual.value
+      if value.is_a?(String) || value.responds_to?(:ends_with?)
+        negated_match_ends_with(value, actual.label)
      else
-        negated_match_last(actual)
+        negated_match_last(value, actual.label)
      end
    end

@ -44,9 +46,9 @@ module Spectator::Matchers
    # This method expects (and uses) the `#ends_with?` method on the value.
    private def match_ends_with(actual_value, actual_label)
      if actual_value.ends_with?(expected.value)
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual_label} does not end with #{expected.label} (using #ends_with?)",
+        FailedMatchData.new(description, "#{actual_label} does not end with #{expected.label} (using #ends_with?)",
          expected: expected.value.inspect,
          actual: actual_value.inspect
        )
@ -60,9 +62,9 @@ module Spectator::Matchers
      last = list.last

      if expected.value === last
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual_label} does not end with #{expected.label} (using expected === last)",
+        FailedMatchData.new(description, "#{actual_label} does not end with #{expected.label} (using expected === last)",
          expected: expected.value.inspect,
          actual: last.inspect,
          list: list.inspect
@ -72,31 +74,31 @@ module Spectator::Matchers

    # Checks whether the actual value does not end with the expected value.
    # This method expects (and uses) the `#ends_with?` method on the value.
-    private def negated_match_ends_with(actual)
-      if actual.value.ends_with?(expected.value)
-        FailedMatchData.new("#{actual.label} ends with #{expected.label} (using #ends_with?)",
-          expected: expected.value.inspect,
-          actual: actual.value.inspect
+    private def negated_match_ends_with(actual_value, actual_label)
+      if actual_value.ends_with?(expected.value)
+        FailedMatchData.new(description, "#{actual_label} ends with #{expected.label} (using #ends_with?)",
+          expected: "Not #{expected.value.inspect}",
+          actual: actual_value.inspect
        )
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end

    # Checks whether the last element of the value is not the expected value.
    # This method expects that the actual value is a set (enumerable).
-    private def negated_match_last(actual)
-      list = actual.value.to_a
+    private def negated_match_last(actual_value, actual_label)
+      list = actual_value.to_a
      last = list.last

      if expected.value === last
-        FailedMatchData.new("#{actual.label} ends with #{expected.label} (using expected === last)",
-          expected: expected.value.inspect,
+        FailedMatchData.new(description, "#{actual_label} ends with #{expected.label} (using expected === last)",
+          expected: "Not #{expected.value.inspect}",
          actual: last.inspect,
          list: list.inspect
        )
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end
  end
--- a/src/spectator/matchers/exception_matcher.cr
+++ b/src/spectator/matchers/exception_matcher.cr
@ -33,16 +33,16 @@ module Spectator::Matchers
    def match(actual : TestExpression(T)) : MatchData forall T
      exception = capture_exception { actual.value }
      if exception.nil?
-        FailedMatchData.new("#{actual.label} did not raise", expected: ExceptionType.inspect)
+        FailedMatchData.new(description, "#{actual.label} did not raise", expected: ExceptionType.inspect)
      else
        if exception.is_a?(ExceptionType)
          if (value = expected.value).nil?
-            SuccessfulMatchData.new
+            SuccessfulMatchData.new(description)
          else
            if value === exception.message
-              SuccessfulMatchData.new
+              SuccessfulMatchData.new(description)
            else
-              FailedMatchData.new("#{actual.label} raised #{exception.class}, but the message is not #{expected.label}",
+              FailedMatchData.new(description, "#{actual.label} raised #{exception.class}, but the message is not #{expected.label}",
                "expected type": ExceptionType.inspect,
                "actual type": exception.class.inspect,
                "expected message": value.inspect,
@ -51,7 +51,7 @@ module Spectator::Matchers
            end
          end
        else
-          FailedMatchData.new("#{actual.label} did not raise #{ExceptionType}",
+          FailedMatchData.new(description, "#{actual.label} did not raise #{ExceptionType}",
            expected: ExceptionType.inspect,
            actual: exception.class.inspect
          )
@ -64,32 +64,37 @@ module Spectator::Matchers
    def negated_match(actual : TestExpression(T)) : MatchData forall T
      exception = capture_exception { actual.value }
      if exception.nil?
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
        if exception.is_a?(ExceptionType)
          if (value = expected.value).nil?
-            FailedMatchData.new("#{actual.label} raised #{exception.class}",
+            FailedMatchData.new(description, "#{actual.label} raised #{exception.class}",
              expected: "Not #{ExceptionType}",
              actual: exception.class.inspect
            )
          else
            if value === exception.message
-              FailedMatchData.new("#{actual.label} raised #{exception.class} with message matching #{expected.label}",
+              FailedMatchData.new(description, "#{actual.label} raised #{exception.class} with message matching #{expected.label}",
                "expected type": ExceptionType.inspect,
                "actual type": exception.class.inspect,
                "expected message": value.inspect,
                "actual message": exception.message.to_s
              )
            else
-              SuccessfulMatchData.new
+              SuccessfulMatchData.new(description)
            end
          end
        else
-          SuccessfulMatchData.new
+          SuccessfulMatchData.new(description)
        end
      end
    end

+    def with_message(message : T) forall T
+      value = TestValue.new(message)
+      ExceptionMatcher(ExceptionType, T).new(value)
+    end
+
    # Runs a block of code and returns the exception it threw.
    # If no exception was thrown, *nil* is returned.
    private def capture_exception
--- a/src/spectator/matchers/failed_match_data.cr
+++ b/src/spectator/matchers/failed_match_data.cr
@ -15,11 +15,13 @@ module Spectator::Matchers
    getter values : Array(Tuple(Symbol, String))

    # Creates the match data.
-    def initialize(@failure_message, @values)
+    def initialize(description, @failure_message, @values)
+      super(description)
    end

    # Creates the match data.
-    def initialize(@failure_message, **values)
+    def initialize(description, @failure_message, **values)
+      super(description)
      @values = values.to_a
    end
  end
--- a/src/spectator/matchers/have_predicate_matcher.cr
+++ b/src/spectator/matchers/have_predicate_matcher.cr
@ -7,13 +7,6 @@ module Spectator::Matchers
  # Each key in the tuple is a predicate (without the '?' and 'has_' prefix) to test.
  # Each value is a a `Tuple` of arguments to pass to the predicate method.
  struct HavePredicateMatcher(ExpectedType) < ValueMatcher(ExpectedType)
-    # Expected value and label.
-    private getter expected
-
-    # Creates the matcher with a expected values.
-    def initialize(@expected : TestValue(ExpectedType))
-    end
-
    # Short text about the matcher's purpose.
    # This explains what condition satisfies the matcher.
    # The description is used when the one-liner syntax is used.
@ -25,9 +18,9 @@ module Spectator::Matchers
    def match(actual : TestExpression(T)) : MatchData forall T
      snapshot = snapshot_values(actual.value)
      if match?(snapshot)
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual.label} does not have #{expected.label}", **values(snapshot))
+        FailedMatchData.new(description, "#{actual.label} does not have #{expected.label}", **values(snapshot))
      end
    end

@ -36,9 +29,9 @@ module Spectator::Matchers
    def negated_match(actual : TestExpression(T)) : MatchData forall T
      snapshot = snapshot_values(actual.value)
      if match?(snapshot)
-        FailedMatchData.new("#{actual.label} has #{expected.label}", **values(snapshot))
+        FailedMatchData.new(description, "#{actual.label} has #{expected.label}", **values(snapshot))
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end

--- a/src/spectator/matchers/instance_matcher.cr
+++ b/src/spectator/matchers/instance_matcher.cr
@ -0,0 +1,57 @@
+require "./matcher"
+
+module Spectator::Matchers
+  # Matcher that tests a value is of a specified type.
+  struct InstanceMatcher(Expected) < StandardMatcher
+    # Short text about the matcher's purpose.
+    # This explains what condition satisfies the matcher.
+    # The description is used when the one-liner syntax is used.
+    def description : String
+      "is an instance of #{Expected}"
+    end
+
+    # Checks whether the matcher is satisifed with the expression given to it.
+    private def match?(actual : TestExpression(T)) : Bool forall T
+      actual.value.class == Expected
+    end
+
+    # Message displayed when the matcher isn't satisifed.
+    #
+    # This is only called when `#match?` returns false.
+    #
+    # The message should typically only contain the test expression labels.
+    # Actual values should be returned by `#values`.
+    private def failure_message(actual) : String
+      "#{actual.label} is not an instance of #{Expected}"
+    end
+
+    # Message displayed when the matcher isn't satisifed and is negated.
+    # This is essentially what would satisfy the matcher if it wasn't negated.
+    #
+    # This is only called when `#does_not_match?` returns false.
+    #
+    # The message should typically only contain the test expression labels.
+    # Actual values should be returned by `#values`.
+    private def failure_message_when_negated(actual) : String
+      "#{actual.label} is an instance of #{Expected}"
+    end
+
+    # Additional information about the match failure.
+    # The return value is a NamedTuple with Strings for each value.
+    private def values(actual)
+      {
+        expected: Expected.to_s,
+        actual:   actual.value.class.inspect,
+      }
+    end
+
+    # Additional information about the match failure when negated.
+    # The return value is a NamedTuple with Strings for each value.
+    private def negated_values(actual)
+      {
+        expected: "Not #{Expected}",
+        actual:   actual.value.class.inspect,
+      }
+    end
+  end
+end
--- a/src/spectator/matchers/match_data.cr
+++ b/src/spectator/matchers/match_data.cr
@ -3,5 +3,10 @@ module Spectator::Matchers
  abstract struct MatchData
    # Indicates whether the match as successful or not.
    abstract def matched? : Bool
+
+    getter description : String
+
+    def initialize(@description : String)
+    end
  end
 end
--- a/src/spectator/matchers/predicate_matcher.cr
+++ b/src/spectator/matchers/predicate_matcher.cr
@ -24,9 +24,9 @@ module Spectator::Matchers
    def match(actual : TestExpression(T)) : MatchData forall T
      snapshot = snapshot_values(actual.value)
      if match?(snapshot)
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual.label} is not #{expected.label}", **values(snapshot))
+        FailedMatchData.new(description, "#{actual.label} is not #{expected.label}", **values(snapshot))
      end
    end

@ -35,9 +35,9 @@ module Spectator::Matchers
    def negated_match(actual : TestExpression(T)) : MatchData forall T
      snapshot = snapshot_values(actual.value)
      if match?(snapshot)
-        FailedMatchData.new("#{actual.label} is #{expected.label}", **values(snapshot))
+        FailedMatchData.new(description, "#{actual.label} is #{expected.label}", **values(snapshot))
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end

--- a/src/spectator/matchers/range_matcher.cr
+++ b/src/spectator/matchers/range_matcher.cr
@ -13,6 +13,7 @@ module Spectator::Matchers

    # Returns a new matcher, with the same bounds, but uses an inclusive range.
    def inclusive
+      label = expected.label
      new_range = Range.new(range.begin, range.end, exclusive: false)
      expected = TestValue.new(new_range, label)
      RangeMatcher.new(expected)
@ -20,6 +21,7 @@ module Spectator::Matchers

    # Returns a new matcher, with the same bounds, but uses an exclusive range.
    def exclusive
+      label = expected.label
      new_range = Range.new(range.begin, range.end, exclusive: true)
      expected = TestValue.new(new_range, label)
      RangeMatcher.new(expected)
--- a/src/spectator/matchers/reference_matcher.cr
+++ b/src/spectator/matchers/reference_matcher.cr
@ -13,7 +13,13 @@ module Spectator::Matchers

    # Checks whether the matcher is satisifed with the expression given to it.
    private def match?(actual : TestExpression(T)) : Bool forall T
-      expected.value.same?(actual.value)
+      value = expected.value
+      if value.responds_to?(:same?)
+        value.same?(actual.value)
+      else
+        # Value type (struct) comparison.
+        actual.value.class == value.class && actual.value == value
+      end
    end

    # Message displayed when the matcher isn't satisifed.
--- a/src/spectator/matchers/respond_matcher.cr
+++ b/src/spectator/matchers/respond_matcher.cr
@ -16,10 +16,10 @@ module Spectator::Matchers
    # Actually performs the test against the expression.
    def match(actual : TestExpression(T)) : MatchData forall T
      snapshot = snapshot_values(actual.value)
-      if match?(snapshot)
-        SuccessfulMatchData.new
+      if snapshot.values.all?
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual.label} does not respond to #{label}", **values(snapshot))
+        FailedMatchData.new(description, "#{actual.label} does not respond to #{label}", **values(snapshot))
      end
    end

@ -27,10 +27,10 @@ module Spectator::Matchers
    # A successful match with `#match` should normally fail for this method, and vice-versa.
    def negated_match(actual : TestExpression(T)) : MatchData forall T
      snapshot = snapshot_values(actual.value)
-      if match?(snapshot)
-        FailedMatchData.new("#{actual.label} responds to #{label}", **values(snapshot))
+      if snapshot.values.any?
+        FailedMatchData.new(description, "#{actual.label} responds to #{label}", **values(snapshot))
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end

@ -46,13 +46,6 @@ module Spectator::Matchers
      {% end %}
    end

-    # Checks if all results from the snapshot are satisified.
-    private def match?(snapshot)
-      # The snapshot did the hard work.
-      # Here just check if all values are true.
-      snapshot.values.all?
-    end
-
    # Produces the tuple for the failed match data from a snapshot of the results.
    private def values(snapshot)
      {% begin %}
--- a/src/spectator/matchers/standard_matcher.cr
+++ b/src/spectator/matchers/standard_matcher.cr
@ -25,9 +25,9 @@ module Spectator::Matchers
    # Additionally, `#failure_message` and `#values` are called for a failed match.
    def match(actual : TestExpression(T)) : MatchData forall T
      if match?(actual)
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new(failure_message(actual), values(actual).to_a)
+        FailedMatchData.new(description, failure_message(actual), values(actual).to_a)
      end
    end

@ -39,10 +39,11 @@ module Spectator::Matchers
    # Otherwise, a `FailedMatchData` instance is returned.
    # Additionally, `#failure_message_when_negated` and `#negated_values` are called for a failed match.
    def negated_match(actual : TestExpression(T)) : MatchData forall T
+      # TODO: Invert description.
      if does_not_match?(actual)
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new(failure_message_when_negated(actual), negated_values(actual).to_a)
+        FailedMatchData.new(description, failure_message_when_negated(actual), negated_values(actual).to_a)
      end
    end

--- a/src/spectator/matchers/start_with_matcher.cr
+++ b/src/spectator/matchers/start_with_matcher.cr
@ -22,7 +22,8 @@ module Spectator::Matchers

    # Actually performs the test against the expression.
    def match(actual : TestExpression(T)) : MatchData forall T
-      if (value = actual.value).responds_to?(:starts_with?)
+      value = actual.value
+      if value.is_a?(String) || value.responds_to?(:starts_with?)
        match_starts_with(value, actual.label)
      else
        match_first(value, actual.label)
@ -32,7 +33,8 @@ module Spectator::Matchers
    # Performs the test against the expression, but inverted.
    # A successful match with `#match` should normally fail for this method, and vice-versa.
    def negated_match(actual : TestExpression(T)) : MatchData forall T
-      if (value = actual.value).responds_to?(:starts_with?)
+      value = actual.value
+      if value.is_a?(String) || value.responds_to?(:starts_with?)
        negated_match_starts_with(value, actual.label)
      else
        negated_match_first(value, actual.label)
@ -43,9 +45,9 @@ module Spectator::Matchers
    # This method expects (and uses) the `#starts_with?` method on the value.
    private def match_starts_with(actual_value, actual_label)
      if actual_value.starts_with?(expected.value)
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual_label} does not start with #{expected.label} (using #starts_with?)",
+        FailedMatchData.new(description, "#{actual_label} does not start with #{expected.label} (using #starts_with?)",
          expected: expected.value.inspect,
          actual: actual_value.inspect
        )
@ -59,9 +61,9 @@ module Spectator::Matchers
      first = list.first

      if expected.value === first
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual_label} does not start with #{expected.label} (using expected === first)",
+        FailedMatchData.new(description, "#{actual_label} does not start with #{expected.label} (using expected === first)",
          expected: expected.value.inspect,
          actual: first.inspect,
          list: list.inspect
@ -73,12 +75,12 @@ module Spectator::Matchers
    # This method expects (and uses) the `#starts_with?` method on the value.
    private def negated_match_starts_with(actual_value, actual_label)
      if actual_value.starts_with?(expected.value)
-        FailedMatchData.new("#{actual_label} starts with #{expected.label} (using #starts_with?)",
-          expected: expected.value.inspect,
+        FailedMatchData.new(description, "#{actual_label} starts with #{expected.label} (using #starts_with?)",
+          expected: "Not #{expected.value.inspect}",
          actual: actual_value.inspect
        )
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end

@ -89,13 +91,13 @@ module Spectator::Matchers
      first = list.first

      if expected.value === first
-        FailedMatchData.new("#{actual_label} starts with #{expected.label} (using expected === first)",
-          expected: expected.value.inspect,
+        FailedMatchData.new(description, "#{actual_label} starts with #{expected.label} (using expected === first)",
+          expected: "Not #{expected.value.inspect}",
          actual: first.inspect,
          list: list.inspect
        )
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end
  end
--- a/src/spectator/matchers/type_matcher.cr
+++ b/src/spectator/matchers/type_matcher.cr
@ -8,7 +8,7 @@ module Spectator::Matchers
    # This explains what condition satisfies the matcher.
    # The description is used when the one-liner syntax is used.
    def description : String
-      "is as #{Expected}"
+      "is a #{Expected}"
    end

    # Checks whether the matcher is satisifed with the expression given to it.
--- a/src/spectator/matchers/unordered_array_matcher.cr
+++ b/src/spectator/matchers/unordered_array_matcher.cr
@ -25,9 +25,9 @@ module Spectator::Matchers
      missing, extra = array_diff(expected_elements, actual_elements)

      if missing.empty? && extra.empty?
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      else
-        FailedMatchData.new("#{actual_label} does not contain #{expected.label} (unordered)",
+        FailedMatchData.new(description, "#{actual_label} does not contain #{expected.label} (unordered)",
          expected: expected_elements.inspect,
          actual: actual_elements.inspect,
          missing: missing.inspect,
@ -44,12 +44,12 @@ module Spectator::Matchers
      missing, extra = array_diff(expected_elements, actual_elements)

      if missing.empty? && extra.empty?
-        FailedMatchData.new("#{actual_label} contains #{expected.label} (unordered)",
+        FailedMatchData.new(description, "#{actual_label} contains #{expected.label} (unordered)",
          expected: "Not #{expected_elements.inspect}",
          actual: actual_elements.inspect,
        )
      else
-        SuccessfulMatchData.new
+        SuccessfulMatchData.new(description)
      end
    end

--- a/src/spectator/mocks/double.cr
+++ b/src/spectator/mocks/double.cr
@ -17,13 +17,28 @@ module Spectator::Mocks
          named = false
          name = definition.name.id
          params = definition.args
+
+          # Possibly a weird compiler bug, but syntax like this:
+          # stub instance.==(other) { true }
+          # Results in `other` being the call `other { true }`.
+          # This works around the issue by pulling out the block
+          # and setting the parameter to just the name.
+          if params.last.is_a?(Call)
+            body = params.last.block
+            params[-1] = params.last.name
+          end
+
          args = params.map do |p|
            n = p.is_a?(TypeDeclaration) ? p.var : p.id
            r = named ? "#{n}: #{n}".id : n
            named = true if n.starts_with?('*')
            r
          end
+
+          # The unless is here because `||=` can't be used in macros @_@
+          unless body
            body = definition.block.is_a?(Nop) ? block : definition.block
+          end
        elsif definition.is_a?(TypeDeclaration) # stub foo : Symbol
          name = definition.var
          params = [] of MacroId
--- a/src/spectator/mocks/stubs.cr
+++ b/src/spectator/mocks/stubs.cr
@ -12,13 +12,19 @@ module Spectator::Mocks
          named = false
          name = definition.name.id
          params = definition.args
+          if params.last.is_a?(Call)
+            body = params.last.block
+            params[-1] = params.last.name
+          end
          args = params.map do |p|
            n = p.is_a?(TypeDeclaration) ? p.var : p.id
            r = named ? "#{n}: #{n}".id : n
            named = true if n.starts_with?('*')
            r
          end
+          unless body
            body = definition.block.is_a?(Nop) ? block : definition.block
+          end
        elsif definition.is_a?(TypeDeclaration) # stub foo : Symbol
          name = definition.var
          params = [] of MacroId
@ -28,17 +34,19 @@ module Spectator::Mocks
          raise "Unrecognized stub format"
        end

-        original = if @type.methods.find { |m| m.name.id == name }
-                     :previous_def
-                   else
-                     :super
-                   end.id
+        t = @type
        receiver = if receiver == :self.id
-                     original = :previous_def.id
+                     t = t.class
                     "self."
                   else
                     ""
                   end.id
+        original = if (name == :new.id && receiver == "self.".id) ||
+                      (t.superclass.has_method?(name) && !t.overrides?(t.superclass, name))
+                     :super
+                   else
+                     :previous_def
+                   end.id
      %}

      {% if body && !body.is_a?(Nop) %}
--- a/src/spectator/runnable_example.cr
+++ b/src/spectator/runnable_example.cr
@ -19,6 +19,7 @@ module Spectator
      ResultCapture.new.tap do |result|
        context.run_before_hooks(self)
        run_example(result)
+        @finished = true
        context.run_after_hooks(self)
        run_deferred(result) unless result.error
      end
--- a/src/spectator/spec_builder.cr
+++ b/src/spectator/spec_builder.cr
@ -42,7 +42,7 @@ module Spectator
    # Adds an example type to the current group.
    # The class name of the example should be passed as an argument.
    # The example will be instantiated later.
-    def add_example(description : String, source : Source,
+    def add_example(description : String?, source : Source,
                    example_type : ::SpectatorTest.class, &runner : ::SpectatorTest ->) : Nil
      builder = ->(values : TestValues) { example_type.new(values).as(::SpectatorTest) }
      factory = RunnableExampleBuilder.new(description, source, builder, runner)
@ -52,7 +52,7 @@ module Spectator
    # Adds an example type to the current group.
    # The class name of the example should be passed as an argument.
    # The example will be instantiated later.
-    def add_pending_example(description : String, source : Source,
+    def add_pending_example(description : String?, source : Source,
                            example_type : ::SpectatorTest.class, &runner : ::SpectatorTest ->) : Nil
      builder = ->(values : TestValues) { example_type.new(values).as(::SpectatorTest) }
      factory = PendingExampleBuilder.new(description, source, builder, runner)
--- a/src/spectator/spec_builder/example_builder.cr
+++ b/src/spectator/spec_builder/example_builder.cr
@ -6,7 +6,7 @@ module Spectator::SpecBuilder
  abstract class ExampleBuilder
    alias FactoryMethod = TestValues -> ::SpectatorTest

-    def initialize(@description : String, @source : Source, @builder : FactoryMethod, @runner : TestMethod)
+    def initialize(@description : String?, @source : Source, @builder : FactoryMethod, @runner : TestMethod)
    end

    abstract def build(group) : ExampleComponent
--- a/src/spectator/test_wrapper.cr
+++ b/src/spectator/test_wrapper.cr
@ -8,13 +8,19 @@ module Spectator
  # Used to instantiate tests and run them.
  struct TestWrapper
    # Description the user provided for the test.
-    getter description
+    def description
+      @description || @source.to_s
+    end

    # Location of the test in source code.
    getter source

    # Creates a wrapper for the test.
-    def initialize(@description : String, @source : Source, @test : ::SpectatorTest, @runner : TestMethod)
+    def initialize(@description : String?, @source : Source, @test : ::SpectatorTest, @runner : TestMethod)
+    end
+
+    def description?
+      !@description.nil?
    end

    def run
--- a/src/spectator_test.cr
+++ b/src/spectator_test.cr
@ -6,6 +6,14 @@ require "./spectator/dsl"
 class SpectatorTest
  include ::Spectator::DSL

+  def _spectator_implicit_subject
+    nil
+  end
+
+  def subject
+    _spectator_implicit_subject
+  end
+
  def initialize(@spectator_test_values : ::Spectator::TestValues)
  end
 end