diff --git a/spec/helpers/spy_formatter.cr b/spec/helpers/spy_formatter.cr
new file mode 100644
index 0000000..f5e2df0
--- /dev/null
+++ b/spec/helpers/spy_formatter.cr
@@ -0,0 +1,33 @@
+# Formatter that doubles as a spy.
+# This class tracks calls made to it.
+class SpyFormatter < Spectator::Formatters::Formatter
+  {% for item in [
+                   {"start_suite", "Spectator::TestSuite"},
+                   {"end_suite", "Spectator::Report"},
+                   {"start_example", "Spectator::Example"},
+                   {"end_example", "Spectator::Result"},
+                 ] %}
+  {% method_name = item[0].id %}
+  {% argument_type = item[1].id %}
+
+  # Stores all invocations made to `#{{method_name}}`.
+  # Each element is an invocation and the value is the argument passed to the method.
+  getter {{method_name}}_calls = [] of {{argument_type}}
+
+  # Number of times the `#{{method_name}}` method was called.
+  def {{method_name}}_call_count
+    @{{method_name}}_calls.size
+  end
+
+  # Increments `#{{method_name}}_call_count` and stores the argument.
+  def {{method_name}}(arg : {{argument_type}})
+    @all_calls << {{method_name.symbolize}}
+    @{{method_name}}_calls << arg
+  end
+
+  {% end %}
+
+  # Stores the methods that were called and in which order.
+  # The symbols will be the method name (i.e. `:start_suite`).
+  getter all_calls = [] of Symbol
+end
diff --git a/spec/runner_spec.cr b/spec/runner_spec.cr
new file mode 100644
index 0000000..2965eda
--- /dev/null
+++ b/spec/runner_spec.cr
@@ -0,0 +1,158 @@
+require "./spec_helper"
+
+# Creates a `Config` for Spectator that is suited for testing it.
+def spectator_test_config(formatter : Spectator::Formatters::Formatter? = nil)
+  Spectator::Config.new(formatter || Spectator::Formatters::SilentFormatter.new)
+end
+
+def new_test_suite
+  example = PassingExample.create
+  Spectator::TestSuite.new(example.group)
+end
+
+describe Spectator::Runner do
+  describe "#run" do
+    it "runs all examples in the suite" do
+      called = [] of Int32
+      group = SpyExample.create_group(5) do |index|
+        called << index
+        nil
+      end
+      suite = Spectator::TestSuite.new(group)
+      runner = Spectator::Runner.new(suite, spectator_test_config)
+      runner.run
+      called.should eq([0, 1, 2, 3, 4])
+    end
+
+    context "the formatter" do
+      it "#start_suite is called once" do
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(new_test_suite, spectator_test_config(spy))
+        runner.run
+        spy.start_suite_call_count.should eq(1)
+      end
+
+      it "#start_suite is called at the beginning" do
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(new_test_suite, spectator_test_config(spy))
+        runner.run
+        spy.all_calls.first.should eq(:start_suite)
+      end
+
+      it "passes the test suite to #start_suite" do
+        test_suite = new_test_suite
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(test_suite, spectator_test_config(spy))
+        runner.run
+        spy.start_suite_calls.first.should eq(test_suite)
+      end
+
+      it "#end_suite is called once" do
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(new_test_suite, spectator_test_config(spy))
+        runner.run
+        spy.end_suite_call_count.should eq(1)
+      end
+
+      it "#end_suite is called at the end" do
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(new_test_suite, spectator_test_config(spy))
+        runner.run
+        spy.all_calls.last.should eq(:end_suite)
+      end
+
+      it "#start_example is called" do
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(new_test_suite, spectator_test_config(spy))
+        runner.run
+        spy.start_example_call_count.should be > 0
+      end
+
+      it "#start_example is called for each example" do
+        group = SpyExample.create_group(5) { |index| nil }
+        suite = Spectator::TestSuite.new(group)
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(suite, spectator_test_config(spy))
+        runner.run
+        spy.start_example_call_count.should eq(5)
+      end
+
+      it "passes the correct example to #start_example" do
+        group = SpyExample.create_group(5) { |index| nil }
+        suite = Spectator::TestSuite.new(group)
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(suite, spectator_test_config(spy))
+        runner.run
+        spy.start_example_calls.should eq(group.children)
+      end
+
+      it "calls #end_example" do
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(new_test_suite, spectator_test_config(spy))
+        runner.run
+        spy.end_example_call_count.should be > 0
+      end
+
+      it "calls #end_example for each example" do
+        group = SpyExample.create_group(5) { |index| nil }
+        suite = Spectator::TestSuite.new(group)
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(suite, spectator_test_config(spy))
+        runner.run
+        spy.end_example_call_count.should eq(5)
+      end
+
+      it "passes the correct result to #end_example" do
+        group = Spectator::RootExampleGroup.new(Spectator::ExampleHooks.empty, Spectator::ExampleConditions.empty)
+        group.children = Array.new(5) do |index|
+          if index.odd?
+            PassingExample.new(group, Spectator::Internals::SampleValues.empty)
+          else
+            FailingExample.new(group, Spectator::Internals::SampleValues.empty)
+          end.as(Spectator::ExampleComponent)
+        end
+        suite = Spectator::TestSuite.new(group)
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(suite, spectator_test_config(spy))
+        runner.run
+        spy.end_example_calls.map(&.example).should eq(group.children)
+      end
+    end
+
+    context "the report" do
+      it "contains the expected results" do
+        group = Spectator::RootExampleGroup.new(Spectator::ExampleHooks.empty, Spectator::ExampleConditions.empty)
+        group.children = Array.new(5) do |index|
+          if index.odd?
+            PassingExample.new(group, Spectator::Internals::SampleValues.empty)
+          else
+            FailingExample.new(group, Spectator::Internals::SampleValues.empty)
+          end.as(Spectator::ExampleComponent)
+        end
+        suite = Spectator::TestSuite.new(group)
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(suite, spectator_test_config(spy))
+        runner.run
+        spy.end_example_calls.each_with_index do |result, index|
+          if index.odd?
+            result.should be_a(Spectator::SuccessfulResult)
+          else
+            result.should be_a(Spectator::FailedResult)
+          end
+        end
+      end
+
+      it "contains the expected time span" do
+        group = SpyExample.create_group(5) { |index| nil }
+        suite = Spectator::TestSuite.new(group)
+        spy = SpyFormatter.new
+        runner = Spectator::Runner.new(suite, spectator_test_config(spy))
+        max_time = Time.measure { runner.run }
+        min_time = spy.end_example_calls.sum(&.elapsed)
+        report = spy.end_suite_calls.first
+        report.runtime.should be <= max_time
+        report.runtime.should be >= min_time
+      end
+    end
+  end
+end