Improve Module#undef_method spec to check the message and module name

Author: eregon

spec/ruby/core/module/undef_method_spec.rb

@@ -57,15 +57,36 @@ def another_method_to_undef() 1 end
   end
 
   it "raises a NameError when passed a missing name for a module" do
-    -> { @module.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method `not_exist' for module/) { |e|
+    -> { @module.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method `not_exist' for module `#{@module}'/) { |e|
       # a NameError and not a NoMethodError
       e.class.should == NameError
     }
   end
 
   it "raises a NameError when passed a missing name for a class" do
     klass = Class.new
-    -> { klass.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method `not_exist' for class/) { |e|
+    -> { klass.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method `not_exist' for class `#{klass}'/) { |e|
+      # a NameError and not a NoMethodError
+      e.class.should == NameError
+    }
+  end
+
+  it "raises a NameError when passed a missing name for a singleton class" do
+    klass = Class.new
+    obj = klass.new
+    sclass = obj.singleton_class
+
+    -> { sclass.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method `not_exist' for class `#{sclass}'/) { |e|
+      e.message.should include('`#<Class:#<#<Class:')
+
+      # a NameError and not a NoMethodError
+      e.class.should == NameError
+    }
+  end
+
+  it "raises a NameError when passed a missing name for a metaclass" do
+    klass = String.singleton_class
+    -> { klass.send :undef_method, :not_exist }.should raise_error(NameError, /undefined method `not_exist' for class `String'/) { |e|
       # a NameError and not a NoMethodError
       e.class.should == NameError
     }