Convert tests to gtest

NBonaparterequested to merge
patrick96:gtest-conversion into master

Created by: patrick96

This converts all legacy tests to use googletest. Except for the string test which was already converted in #1237. I will open a new PR, once this and #1237 are merged to remove the legacy testing functions in test.hpp

Closes #127 because we know have a proper testing setup and testing all the things is something we will never achieve so otherwise this issue would just stay open forever

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