adds the concern aproach and explanation

test/parser/helper.rb

@@ -1,29 +1,59 @@
 require_relative "../helper"
 
-module ParserTest
+# Included in parser test will create tests methods
+module ParserHelper
   
-  def setup
-    @parser    = Parser::Composed.new
-    @transform = Parser::Transform.new
+  def self.included(base)
+    base.send :include, InstanceMethods  #provides helpers and setup
+    base.send :extend, ClassMethods   #gets the method creation going
+  end
+ 
+  module InstanceMethods
+    def setup
+      @parser    = Parser::Composed.new
+      @transform = Parser::Transform.new
+    end
+
+    # check that @string_input parses correctly to @parse_output
+    def check_parse
+      is = @parser.parse(@string_input)
+      #puts is.inspect
+      assert_equal @parse_output , is
+    end
+
+    #check that @parse_output transforms to @transform_output
+    def check_transform
+      is = @transform.apply @parse_output
+      #puts is.transform
+      assert_equal @transform_output , is
+    end
+
+    # check that @string_input parses and transforms to @transform_output
+    def check_ast
+      syntax    = @parser.parse(@string_input)
+      tree      = @transform.apply(syntax)
+      # puts tree.inspect
+      assert_equal @transform_output , tree
+    end
   end
 
-  def check_parse
-    is = @parser.parse(@input)
-    #puts is.inspect
-    assert_equal @parse_output , is
-  end
-
-  def check_transform
-    is = @transform.apply @parse_output
-    #puts is.transform
-    assert_equal @transform_output , is
-  end
-
-  def check_ast
-    syntax    = @parser.parse(@input)
-    tree      = @transform.apply(syntax)
-    # puts tree.inspect
-    assert_equal @transform_output , tree
-  end
-    
-end
+  module ClassMethods
+    # this creates test methods dynamically. For each parse_* method we create 
+    # three test_* methods that in turn check the three phases.
+    # runnable_methods is called by minitest to determine which tests to run (ie normally test_*)
+    def runnable_methods
+      tests = []
+      public_instance_methods(true).grep(/^parse_/).map(&:to_s).each do |parse|
+        ["ast" , "transform" , "parse"].each do |what|
+          name = "parse_#{what}"
+          tests << name
+          self.send(:define_method, name ) do
+            send(parse)
+            send("check_#{what}")
+          end
+        end
+      end
+      tests
+    end
+   end
+end