Feature Request: Write some proper unit tests.

[olgasolodovnikova]

Could compare some state prep circuits with strawberryfields.
To avoid importing strawberryfields, could save some data generated from it.
To do: write unit tests of all functions/clases 😫

[olgasolodovnikova]

Added tests/test_base.py where base class is tested, e.g. measurements and gates. Small comparison with strawberryfields simulation (without having to import strawberryfields) is also there.