Add test for redundant module inclusion in a subclass

Author: flvrone

spec/ruby-enum/enum_spec.rb

@@ -17,6 +17,13 @@ class FirstSubclass < Colors
   class SecondSubclass < FirstSubclass
     define :PINK, 'pink'
   end
+
+  class OtherSecondSubclass < FirstSubclass
+    include Ruby::Enum
+
+    define :MAGENTA, 'magenta'
+  end
+
   it 'returns an enum value' do
     expect(Colors::RED).to eq 'red'
     expect(Colors::GREEN).to eq 'green'
@@ -169,6 +176,12 @@ class SecondSubclass < FirstSubclass
         expect(SecondSubclass.values).to eq(%w[red green orange pink])
       end
     end
+
+    context 'when a subclass of a subclass is defined with redundant module inclusion' do
+      it 'returns all values' do
+        expect(OtherSecondSubclass.values).to eq(%w[red green orange magenta])
+      end
+    end
   end
 
   describe '#to_h' do