This test performs animations of the transform property on five boxes over 2 seconds.
Box 1 has all keyframes. Box 2 has a missing "from" keyframe.
Box 3 has a missing "to" keyframe.
Box 4 has both "from" and "to" keyframes missing, but other keyframes which
should trigger the generation of "from" and "to". Box 5 has no keyframes, and
should not animate.
The test takes 3 snapshots each and expects each result to be within a specified range.