Fix random seed
In unit tests random seed is always set to 0. This does not give the same random numbers on different machines. Therefore some commits fail the unit tests eg. 765ab1a9. -> Fix all seeds to a different number, not 0.
(https://stackoverflow.com/questions/42727631/generating-machine-independent-random-numbers-in-python, https://github.com/numpy/numpy/issues/8771)