diff --git a/src/spectator.cr b/src/spectator.cr
index a6708af..89c8306 100644
--- a/src/spectator.cr
+++ b/src/spectator.cr
@@ -95,7 +95,7 @@ module Spectator
   private def run
     # Build the test spec and run it.
     spec = ::Spectator::DSL::Builder.build
-    # Runner.new(suite, config).run
+    spec.run
     true
   rescue ex
     # Catch all unhandled exceptions here.
diff --git a/src/spectator/example.cr b/src/spectator/example.cr
index e5607e2..b395748 100644
--- a/src/spectator/example.cr
+++ b/src/spectator/example.cr
@@ -28,7 +28,7 @@ module Spectator
     # Returns the result of the execution.
     # The result will also be stored in `#result`.
     def run : Result
-      Spectator.debug_out("Running example #{example}")
+      Spectator.debug_out("Running example #{self}")
       @delegate.call(self)
       raise NotImplementedError.new("#run")
     end
diff --git a/src/spectator/example_group.cr b/src/spectator/example_group.cr
index 80b6672..d6d5f84 100644
--- a/src/spectator/example_group.cr
+++ b/src/spectator/example_group.cr
@@ -4,6 +4,7 @@ module Spectator
   # Collection of examples and sub-groups.
   class ExampleGroup < ExampleNode
     include Enumerable(ExampleNode)
+    include Iterable(ExampleNode)
 
     @nodes = [] of ExampleNode
 
@@ -22,6 +23,11 @@ module Spectator
       @nodes.each { |node| yield node }
     end
 
+    # Returns an iterator for each (example and sub-group).
+    def each
+      @nodes.each
+    end
+
     # Checks if all examples and sub-groups have finished.
     def finished? : Bool
       @nodes.all?(&.finished?)
diff --git a/src/spectator/example_iterator.cr b/src/spectator/example_iterator.cr
index b5dd3f3..217f0a0 100644
--- a/src/spectator/example_iterator.cr
+++ b/src/spectator/example_iterator.cr
@@ -1,3 +1,7 @@
+require "./example"
+require "./example_group"
+require "./example_node"
+
 module Spectator
   # Iterates through all examples in a group and its nested groups.
   class ExampleIterator
@@ -5,12 +9,12 @@ module Spectator
 
     # Stack that contains the iterators for each group.
     # A stack is used to track where in the tree this iterator is.
-    @stack : Array(Iterator(ExampleComponent))
+    @stack : Array(Iterator(ExampleNode))
 
     # Creates a new iterator.
     # The *group* is the example group to iterate through.
-    def initialize(@group : Iterable(ExampleComponent))
-      iter = @group.each.as(Iterator(ExampleComponent))
+    def initialize(@group : ExampleGroup)
+      iter = @group.each.as(Iterator(ExampleNode))
       @stack = [iter]
     end
 
@@ -22,8 +26,7 @@ module Spectator
       # b. the stack is empty.
       until @stack.empty?
         # Retrieve the next "thing".
-        # This could be an `Example`,
-        # or a group.
+        # This could be an `Example` or a group.
         item = advance
         # Return the item if it's an example.
         # Otherwise, advance and check the next one.
@@ -36,7 +39,7 @@ module Spectator
     # Restart the iterator at the beginning.
     def rewind
       # Same code as `#initialize`, but return self.
-      iter = @group.each.as(Iterator(ExampleComponent))
+      iter = @group.each.as(Iterator(ExampleNode))
       @stack = [iter]
       self
     end
diff --git a/src/spectator/spec.cr b/src/spectator/spec.cr
index 90a2b6a..17218f9 100644
--- a/src/spectator/spec.cr
+++ b/src/spectator/spec.cr
@@ -1,20 +1,24 @@
 require "./example"
 require "./example_group"
+require "./example_iterator"
 
 module Spectator
+  # Contains examples to be tested.
   class Spec
-    include Enumerable(Example)
-
-    def initialize(@group : ExampleGroup)
+    def initialize(@root : ExampleGroup)
     end
 
-    def each
-      @group.each do |node|
-        if (example = node.as?(Example))
-          yield example
-        elsif (group = node.as?(ExampleGroup))
-          # TODO
-        end
+    def run
+      examples = ExampleIterator.new(@root).to_a
+      Runner.new(examples).run
+    end
+
+    private struct Runner
+      def initialize(@examples : Array(Example))
+      end
+
+      def run
+        @examples.each(&.run)
       end
     end
   end