Tests that the value of the 'class' attribute is included in the DOM,
including space-separated values, and values with extraneous spaces.
The rendered picture should match the reference image, except for
possible variations in the labelling text (per CSS2 rules). The pass
condition is seeing three green circles, with text below each circle
reflecting the normalized space-separated values for the class of that
circle. The leftmost circle has the value "foo", the middle circle has
the value "bar baz", and the rightmost circle has the value
" funky spacing ", normalized to "funky spacing". If any of the
circles are red, the test has failed.
