Fixed buggy test
Fixed buggy test

The test I added previously is incorrect because in Python the equation
"float('NaN') == float('NaN')"
returns False.
I use math.isnan now to check whether a float represents NaN.

kachick/topaz,babelsberg/babelsberg-r,kachick/topaz,topazproject/topaz,topazproject/topaz,kachick/topaz,babelsberg/babelsberg-r,topazproject/topaz,babelsberg/babelsberg-r,topazproject/topaz,babelsberg/babelsberg-r,babelsberg/babelsberg-r