This usually means that the user mixed up our lowercase/uppercase naming convention; see https://github.com/facebook/react/pull/3429#issuecomment-85166440.

We could add a message like

> Warning: The tag <commentBox> is unrecognized in this browser. If you meant to render a React component, start its name with an uppercase letter.

We'd check this only once per tag and only in development mode.

matches = console.error.calls.argsFor(1)[0].match(/.*\(.*:(\d+)\).*/);
      var currentLine = matches[1];
      
      
      expect(parseInt(previousLine, 10) + 12).toBe(parseInt(currentLine, 10));
    });
    it('should suggest property name if available', () => {
      spyOn(console, 'error');
      ReactTestUtils.renderIntoDocument(
        React.createElement('label', {for: 'test'}),
      );
      ReactTestUtils.renderIntoDocument(
        React.createElement('input', {type: 'text', autofocus: true}),
      );
      expectDev(console.error.calls.count()).toBe(2);
      expectDev(console.error.calls.argsFor(0)[0]).toBe(
        'Warning: Unknown DOM property for. Did you mean htmlFor?\n    in label',
      );
      expectDev(console.error.calls.argsFor(1)[0]).toBe(
        'Warning: Unknown DOM property autofocus. Did you mean autoFocus?\n    in input',
      );
    });
    it('should suggest property name if available (ssr)', () => {
      spyOn(console, 'error');
      ReactDOMServer.renderToString(
        React.createElement('label', {for: 'test'}),
      );
      ReactDOMServer.renderToString(
        React.createElement('input', {type: 'text', autofocus: true}),
      );