Weird diff with style attribute

[pawelgalazka]

AcademyProgressBar should render as 67% done when two out of three assignments are done:
     Error:
expected <div class="progress" data-reactid=".0.0.0" style="width: 67%; : "></div>
to have attribute { style: { width: '37%' } }

<div class="progress" style="width: 67%; : undefined" // expected { width: '67%', '': undefined } to satisfy { width: '37%' }
                                                      //
                                                      // {
                                                      //   width: '67%', // should equal '37%'
                                                      //                 // -67%
                                                      //                 // +37%
                                                      //   '': undefined
                                                      // }
     data-reactid=".0.0.0"></div>
      at Context.<anonymous> (app/assets/javascripts/components/AcademyProgressBar/AcademyProgressBar-mocha.jsx:76:5)

    expect(instance.refs['progress'].getDOMNode(), 'to have attribute', {
      style: {
        width: '37%'
      }
    });