Add test for protected methods on module included

Merged: https://github.com/ruby/ruby/pull/5642

test/ruby/test_module.rb

@@ -756,6 +756,25 @@ class TestModule < Test::Unit::TestCase
     assert_equal([:m1, :m0, :m, :sc, :m1, :m0, :c], sc.new.m)
   end
 
+  def test_protected_include_into_included_module
+    m1 = Module.new do
+      def other_foo(other)
+        other.foo
+      end
+
+      protected
+      def foo
+        :ok
+      end
+    end
+    m2 = Module.new
+    c1 = Class.new { include m2 }
+    c2 = Class.new { include m2 }
+    m2.include(m1)
+
+    assert_equal :ok, c1.new.other_foo(c2.new)
+  end
+
   def test_instance_methods
     assert_equal([:user, :user2], User.instance_methods(false).sort)
     assert_equal([:user, :user2, :mixin].sort, User.instance_methods(true).sort)