The error event on `<source>` elements doesn't work. Looking at #4370, it seems like there is an `onError` for `<video>` but I can't tell if that's supposed to work for `<source>` too.

The error event is useful so I can deduce which format the browser is using.

);
    });
    it('warns on invalid nesting at root', () => {
      spyOn(console, 'error');
      var p = document.createElement('p');
      ReactDOM.render(<span><p /></span>, p);
      expect(console.error.calls.count()).toBe(1);
      expect(console.error.calls.argsFor(0)[0]).toBe(
        'Warning: validateDOMNesting(...): <p> cannot appear as a descendant ' +
        'of <p>. See p > ... > p.'
      );
    });
    it('warns nicely for table rows', () => {
      spyOn(console, 'error');
      var Row = React.createClass({
        render: function() {
          return <tr />;
        },
      });
      var Foo = React.createClass({
        render: function() {
          return <table><Row /> </table>;
        },
      });
      ReactTestUtils.renderIntoDocument(<Foo />);
      expect(console.error.calls.count()).toBe(2);
      expect(console.error.calls.argsFor(0)[0]).toBe(
        'Warning: validateDOMNesting(...): <tr> cannot appear as a child of ' +
        '<table>. See Foo > table > Row > tr. Add a <tbody> to your code to ' +
        'match the DOM tree generated by the browser.'