* What we care about is the <pre>. The class="CodeMirror-line" is
added to every <pre>. We don't really learn anything new when we
include it in our tests.
* Testing the ARIA role is testing a CodeMirror feature, not a
feature of the mediawiki mode under test.
Change-Id: I33bfedb304228240c4e835cc983117668c398c61
Basic tests to show that the highlighting classes have been attached
to the expected elements.
TODO in later patches:
* tests for the wikitext 2017 editor
Bug: T270240
Change-Id: I01ebd9881d38dd877f19ee3bb4fdcbb74d43afaf
