Add more specific warning assertion for React DOM factories

Author: nhunzaker

src/addons/__tests__/ReactDOMFactories-test.js

@@ -19,7 +19,7 @@ describe('ReactDOMFactories', () => {
     spyOn(console, 'error');
     var element = div();
     expect(element.type).toBe('div');
-    expectDev(console.error.calls.count()).toBe(0);
+    expectDev(console.error).not.toHaveBeenCalled();
   });
 
   it('warns once when accessing React.DOM methods', () => {
@@ -31,6 +31,9 @@ describe('ReactDOMFactories', () => {
     expect(a.type).toBe('a');
     expect(p.type).toBe('p');
 
-    expectDev(console.error.calls.count()).toBe(1);
+    expectDev(console.error).toHaveBeenCalledTimes(1);
+    expectDev(console.error.calls.first().args[0]).toContain(
+      'Warning: Accessing factories like React.DOM.a has been deprecated'
+    );
   });
 });