We just test that their class systems work properly with React:<p><a href="https:&#x2F;&#x2F;github.com&#x2F;facebook&#x2F;react&#x2F;tree&#x2F;v0.14.0-rc1&#x2F;src&#x2F;isomorphic&#x2F;modern&#x2F;class&#x2F;__tests__" rel="nofollow">https:&#x2F;&#x2F;github.com&#x2F;facebook&#x2F;react&#x2F;tree&#x2F;v0.14.0-rc1&#x2F;src&#x2F;isomo...</a><p>We don&#x27;t use either one outside of the tests.