Tests for loop using BitmapClip #1368

[somstrom]

I added some tests for loops using BitmapClip and they passed.

• I have added suitable tests demonstrating a fixed bug or new/changed feature to the test suite in tests/
• I have properly documented new or changed features in the documentation or in the docstrings
• I have formatted my code using black -t py36

[coveralls]

Coverage increased (+0.07%) to 67.525% when pulling 6e1e09c on somstrom:loop-tests into 344aa04 on Zulko:master.

[tburrows13]

These tests are great. However, I'd like to ask that you keep the original 3 tests as well (you can comment out the failing ones). The reason that the they fail is because they include audio and mask clips, which are not replicated in the BitmapClip tests (I suppose that they could be, but I've never done that, so I wouldn't have expected you to!).

[somstrom]

I added test for infinite loop and tests for fadein using BitmapClip

[somstrom]

I would like to fix loop issue, so I got one question.

Loop function is called 2 times so previous_duration is rewritten. But i can't figure out why it is called 2 times. So my question is why is loop function called 2 times.

I have replaced previous_duration with numeric value of clip duration and it works.

[tburrows13]

Check the Gitter for discussion - someone else is also working on it :)

[tburrows13]

Good job, I'm happy to merge.