Add failing test for isMemo bug (#2390)

Author: bdwain

packages/enzyme-test-suite/test/ShallowWrapper-spec.jsx

@@ -5,6 +5,7 @@ import sinon from 'sinon-sandbox';
 import wrap from 'mocha-wrap';
 import isEqual from 'lodash.isequal';
 import inspect from 'object-inspect';
+import { isMemo } from 'react-is';
 
 import {
   shallow,
@@ -1722,6 +1723,11 @@ describe('shallow', () => {
 </div>`);
         expect(() => wrapper.dive().dive()).to.throw(TypeError);
       });
+
+      it('is still marked as memoized after going through the wrapper', () => {
+        const wrapper = shallow(<RendersAppMemoized />);
+        expect(isMemo(wrapper.get(0))).toBe(true);
+      });
     });
   });