STCC-311 Todo in test_converter.py: fix/reorganize test [TN]

[TauBossss]

The tests were very old, i refactored them, so that they test the functionality of the current program. One function is still commented out, i couldnt fix the function, because the svg to png conversion does not work on my pc -couldnt figure out why- and im more or less the last team member at this point.

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