Playing around with inheritance vs. inclusion

inheritance_test.rb

require 'minitest/spec'
require 'minitest/autorun'

describe "class inheritance" do
  it "inherits public singleton methods" do
    superclass = Class.new
    superclass.define_singleton_method(:pub_sing_meth) {}
    subclass = Class.new(superclass)
    subclass.singleton_methods.include?(:pub_sing_meth).must_equal true
  end

  it "does not inherit private singleton methods" do
    superclass = Class.new
    superclass.define_singleton_method(:priv_sing_meth) {}
    superclass.singleton_class.__send__(:private, :priv_sing_meth)
    subclass = Class.new(superclass)
    subclass.singleton_methods.include?(:priv_sing_meth).must_equal false
  end
end

describe "module inclusion" do
  it "defines instance methods from the inherited module" do
    test_module = Module.new { define_method(:imeth) {} }
    test_class = Class.new { include test_module }
    test_class.instance_methods.include?(:imeth).must_equal true
  end

  it "does not define the module's public singleton methods" do
    test_module = Module.new { define_singleton_method(:pub_sing_meth) {} }
    test_class = Class.new { include test_module }
    test_class.singleton_methods.include?(:pub_sing_meth).must_equal false
  end
end

$ ruby inheritance_test.rb 
Loaded suite inheritance_test
Started
....
Finished in 0.000451 seconds.

4 tests, 4 assertions, 0 failures, 0 errors, 0 skips

Test run options: --seed 16536