Add ability to test expectations directly

spec/runtime_example_spec.cr

@@ -28,6 +28,10 @@ Spectator.describe "Runtime compilation" do
     it "does something" do
       expect(true).to be_false
     end
+
+    it "doesn't run" do
+      expect(true).to be_false
+    end
   end
 
   it "detects failed examples" do
@@ -43,4 +47,12 @@ Spectator.describe "Runtime compilation" do
   it "raises on compilation errors" do
     expect { malformed_example }.to raise_error(/compilation/i)
   end
+
+  given_expectation satisfied_expectation do
+    expect(true).to be_true
+  end
+
+  it "can compile and retrieve expectations" do
+    expect(satisfied_expectation).to be_satisfied
+  end
 end

spec/spec_helper.cr

@@ -26,3 +26,21 @@ macro given_example(id, &block)
     ).result
   end
 end
+
+# Defines an example ("it" block) that is lazily compiled.
+# The "it" block must be omitted, as the block provided to this macro will be wrapped in one.
+# When the expectation is referenced with *id*, it will be compiled and the result retrieved.
+# The value returned by *id* will be a `Spectator::SpecHelpers::Expectation`.
+# This allows an expectation to be inspected.
+# Only the last expectation performed will be returned.
+# An error is raised if no expectations ran.
+macro given_expectation(id, &block)
+  let({{id}}) do
+    result = ::Spectator::SpecHelpers::Example.new(
+      {{__FILE__}},
+      {{id.id.stringify}},
+      {{"it do\n" + block.body.stringify + "\nend"}}
+    ).result
+    result.expectations.last || raise("No expectations found from {{id.id}}")
+  end
+end