Pass group to example initializer

src/spectator/dsl/example_factory.cr

@@ -4,8 +4,8 @@ module Spectator
       def initialize(@example_type : Example.class)
       end
 
-      def build(locals : Hash(Symbol, ValueWrapper)) : Example
-        @example_type.new(locals)
+      def build(group : ExampleGroup, locals : Hash(Symbol, ValueWrapper)) : Example
+        @example_type.new(group, locals)
       end
     end
   end

src/spectator/dsl/structure_dsl.cr

@@ -159,10 +159,6 @@ module Spectator
           def description
             {{description.is_a?(StringLiteral) ? description : description.stringify}}
           end
-
-          def group
-            nil # TODO
-          end
         end
 
         ::Spectator::DSL::Builder.add_example(Example%example)

src/spectator/example.cr

@@ -1,12 +1,12 @@
 module Spectator
   abstract class Example
     getter? finished = false
+    getter group : ExampleGroup
 
     abstract def run : Result
     abstract def description : String
-    abstract def group : ExampleGroup
 
-    def initialize(@locals = {} of Symbol => ValueWrapper)
+    def initialize(@group, @locals = {} of Symbol => ValueWrapper)
     end
 
     private getter locals