Restructure to use a composite design pattern

Examples and example groups now have a common ancestor.

src/spectator/dsl/builder.cr

@@ -2,7 +2,7 @@ module Spectator::DSL
   module Builder
     extend self
 
-    @@group_stack = Array(ExampleGroupBuilder).new(1, root_group)
+    @@group_stack = Array(NestedExampleGroupBuilder).new(1, root_group)
 
     private class_getter root_group = RootExampleGroupBuilder.new()
 
@@ -10,13 +10,13 @@ module Spectator::DSL
       @@group_stack.last
     end
 
-    private def push_group(group : ExampleGroupBuilder)
+    private def push_group(group : NestedExampleGroupBuilder)
       current_group.add_child(group)
       @@group_stack.push(group)
     end
 
     def start_group(*args) : Nil
-      group = ::Spectator::DSL::ExampleGroupBuilder.new(*args)
+      group = ::Spectator::DSL::NestedExampleGroupBuilder.new(*args)
       push_group(group)
     end
 

src/spectator/dsl/given_example_group_builder.cr

@@ -1,24 +1,24 @@
-require "./example_group_builder"
+require "./nested_example_group_builder"
 
 module Spectator::DSL
-  class GivenExampleGroupBuilder(T) < ExampleGroupBuilder
+  class GivenExampleGroupBuilder(T) < NestedExampleGroupBuilder
     def initialize(what : String, @collection : Array(T), @symbol : Symbol)
       super(what)
     end
 
-    def build(parent : ExampleGroup?, sample_values : Internals::SampleValues) : ExampleGroup
-      ExampleGroup.new(@what, parent, build_hooks).tap do |group|
+    def build(parent : ExampleGroup, sample_values : Internals::SampleValues) : NestedExampleGroup
+      NestedExampleGroup.new(@what, parent, build_hooks).tap do |group|
         group.children = @collection.map do |value|
-          build_sub_group(group, sample_values, value).as(ExampleGroup::Child)
+          build_sub_group(group, sample_values, value).as(ExampleComponent)
         end
       end
     end
 
-    private def build_sub_group(parent : ExampleGroup, sample_values : Internals::SampleValues, value : T) : ExampleGroup
+    private def build_sub_group(parent : ExampleGroup, sample_values : Internals::SampleValues, value : T) : NestedExampleGroup
       sub_values = sample_values.add(@symbol, @symbol.to_s, value)
-      ExampleGroup.new(value.to_s, parent, ExampleHooks.empty).tap do |group|
+      NestedExampleGroup.new(value.to_s, parent, ExampleHooks.empty).tap do |group|
         group.children = @children.map do |child|
-          child.build(group, sub_values).as(ExampleGroup::Child)
+          child.build(group, sub_values).as(ExampleComponent)
         end
       end
     end

src/spectator/dsl/nested_example_group_builder.cr

@@ -1,6 +1,6 @@
 module Spectator::DSL
-  class ExampleGroupBuilder
-    alias Child = ExampleFactory | ExampleGroupBuilder
+  class NestedExampleGroupBuilder
+    alias Child = ExampleFactory | NestedExampleGroupBuilder
 
     @children = [] of Child
     @before_all_hooks = [] of ->
@@ -36,10 +36,10 @@ module Spectator::DSL
       @around_each_hooks << block
     end
 
-    def build(parent : ExampleGroup?, sample_values : Internals::SampleValues) : ExampleGroup
-      ExampleGroup.new(@what, parent, build_hooks).tap do |group|
+    def build(parent : ExampleGroup, sample_values : Internals::SampleValues) : ExampleGroup
+      NestedExampleGroup.new(@what, parent, build_hooks).tap do |group|
         group.children = @children.map do |child|
-          child.build(group, sample_values).as(ExampleGroup::Child)
+          child.build(group, sample_values).as(ExampleComponent)
         end
       end
     end

src/spectator/dsl/root_example_group_builder.cr

@@ -1,13 +1,13 @@
 module Spectator::DSL
-  class RootExampleGroupBuilder < ExampleGroupBuilder
+  class RootExampleGroupBuilder < NestedExampleGroupBuilder
     def initialize
       super("ROOT")
     end
-    
-    def build(sample_values : Internals::SampleValues) : ExampleGroup
+
+    def build(sample_values : Internals::SampleValues) : RootExampleGroup
       RootExampleGroup.new(build_hooks).tap do |group|
         group.children = @children.map do |child|
-          child.build(group, sample_values).as(ExampleGroup::Child)
+          child.build(group, sample_values).as(ExampleComponent)
         end
       end
     end

src/spectator/example.cr

@@ -1,7 +1,9 @@
+require "./example_component"
+
 module Spectator
   # Base class for all types of examples.
   # Concrete types must implement the `#run_inner` and `#what` methods.
-  abstract class Example
+  abstract class Example < ExampleComponent
     # Indicates whether the example has already been run.
     getter? finished = false
 
@@ -21,9 +23,6 @@ module Spectator
     # Implementation-specific for running the example code.
     private abstract def run_inner : Result
 
-    # Message that describes what the example tests.
-    abstract def what : String
-
     # Creates the base of the example.
     # The group should be the example group the example belongs to.
     # The `sample_values` are passed to the example code.

src/spectator/example_component.cr

@@ -0,0 +1,11 @@
+module Spectator
+  # Abstract base for all examples and collections of examples.
+  # This is used as the base node type for the composite design pattern.
+  abstract class ExampleComponent
+    # Text that describes the context or test.
+    abstract def what : String
+
+    # Indicates whether the example (or group) has been completely run.
+    abstract def finished? : Bool
+  end
+end

src/spectator/example_group.cr

@@ -1,89 +1,82 @@
-require "./example"
+require "./example_component"
 
 module Spectator
-  class ExampleGroup
-    alias Child = Example | ExampleGroup
+  abstract class ExampleGroup < ExampleComponent
+    include Enumerable(ExampleComponent)
+    include Iterable(ExampleComponent)
 
-    getter what : String
-
-    getter! parent : ExampleGroup
-
-    private getter! children : Array(Child)
-    setter children
-
-    def initialize(@what, @parent, @hooks : ExampleHooks)
+    def initialize(@hooks : ExampleHooks)
       @before_all_hooks_run = false
       @after_all_hooks_run = false
     end
 
-    def example_count
-      children.sum do |child|
-        child.is_a?(Example) ? 1 : child.example_count
+    private getter! children : Array(ExampleComponent)
+
+    def children=(children : Array(ExampleComponent))
+      raise "Attempted to reset example group children" if @children
+      @children = children
+    end
+
+    def each
+      children.each do |child|
+        yield child
       end
     end
 
+    def each : Iterator(ExampleComponent)
+      raise NotImplementedError.new("ExampleGroup#each")
+    end
+
+    # TODO: Remove this method.
+    def example_count
+      children.sum do |child|
+        child.is_a?(Example) ? 1 : child.as(ExampleGroup).example_count
+      end
+    end
+
+    # TODO: Remove this method.
     def all_examples
       Array(Example).new(example_count).tap do |array|
         children.each do |child|
           if child.is_a?(Example)
             array << child
           else
-            array.concat(child.all_examples)
+            array.concat(child.as(ExampleGroup).all_examples)
           end
         end
       end
     end
 
-    def run_before_all_hooks
-      if (parent = @parent)
-        parent.run_before_all_hooks
-      end
+    def finished? : Bool
+      children.all?(&.finished?)
+    end
+
+    def run_before_all_hooks : Nil
       unless @before_all_hooks_run
         @hooks.run_before_all
         @before_all_hooks_run = true
       end
     end
 
-    def run_before_each_hooks
-      if (parent = @parent)
-        parent.run_before_each_hooks
-      end
+    def run_before_each_hooks : Nil
       @hooks.run_before_each
     end
 
-    def run_after_all_hooks
+    def run_after_all_hooks : Nil
       unless @after_all_hooks_run
-        if all_examples.all?(&.finished?)
+        if finished?
           @hooks.run_after_all
           @after_all_hooks_run = true
         end
       end
-      if (parent = @parent)
-        parent.run_after_all_hooks
-      end
     end
 
-    def run_after_each_hooks
+    def run_after_each_hooks : Nil
       @hooks.run_after_each
-      if (parent = @parent)
-        parent.run_after_each_hooks
-      end
     end
 
-    def wrap_around_each_hooks(&block : ->)
-      wrapper = @hooks.wrap_around_each(&block)
-      if (parent = @parent)
-        wrapper = parent.wrap_around_each_hooks(&wrapper)
-      end
-      wrapper
-    end
-
-    def to_s(io)
-      if (parent = @parent)
-        parent.to_s(io)
-        io << ' '
-      end
-      io << what
+    def wrap_around_each_hooks(&block : ->) : ->
+      @hooks.wrap_around_each(&block)
     end
   end
 end

src/spectator/includes.cr

@@ -12,12 +12,14 @@ require "./matchers"
 require "./formatters"
 
 # Then all of the top-level types.
+require "./example_component"
 require "./example"
 require "./runnable_example"
 require "./pending_example"
 
 require "./example_hooks"
 require "./example_group"
+require "./nested_example_group"
 require "./root_example_group"
 
 require "./expectation_failed"

src/spectator/nested_example_group.cr

@@ -0,0 +1,57 @@
+require "./example_group"
+
+module Spectator
+  class NestedExampleGroup < ExampleGroup
+    getter what : String
+
+    getter! parent : ExampleGroup
+
+    def initialize(@what, @parent, hooks : ExampleHooks)
+      super(hooks)
+    end
+
+    def run_before_all_hooks : Nil
+      if (parent = @parent)
+        parent.run_before_all_hooks
+      end
+      super
+    end
+
+    def run_before_each_hooks : Nil
+      if (parent = @parent)
+        parent.run_before_each_hooks
+      end
+      super
+    end
+
+    def run_after_all_hooks : Nil
+      super
+      if (parent = @parent)
+        parent.run_after_all_hooks
+      end
+    end
+
+    def run_after_each_hooks : Nil
+      super
+      if (parent = @parent)
+        parent.run_after_each_hooks
+      end
+    end
+
+    def wrap_around_each_hooks(&block : ->) : ->
+      super(&block).tap do |wrapper|
+        if (parent = @parent)
+          wrapper = parent.wrap_around_each_hooks(&wrapper)
+        end
+      end
+    end
+
+    def to_s(io)
+      if (parent = @parent)
+        parent.to_s(io)
+        io << ' '
+      end
+      io << what
+    end
+  end
+end

src/spectator/root_example_group.cr

@@ -2,8 +2,8 @@ require "./example_group"
 
 module Spectator
   class RootExampleGroup < ExampleGroup
-    def initialize(hooks)
-      super("ROOT", nil, hooks)
+    def what : String
+      "ROOT"
     end
 
     def to_s(io)