Testing metric functions

[CosmoMatt]

Add testing metrics to be used for testing package functions

Difficulty:

• Medium

Metric list:

• Mean squared error, this can be used to evaluate round-trip error e.g. x -> x' = inverse( forward( x ) )
• Dot test, this tests whether two transforms are adjoint to one another (see here for a discussion).

S2Wav File location:

• should be put in the test directory here

Notes:

• These metrics should be available to all tests but not shipped as part of the package. The best way to do this is by using Pytest's fixtures api.

[CosmoMatt]

Furthermore, though this is repeated in several other packages now (see e.g. this function) for the sake of brevity we may want to add a function to the test suite that generates random complex and real signals etc.

The sub-issues are thus:

• [ ] Implement mean squared error
• [ ] Implement the dot test for adjoints
• [ ] Write functions to generate arbitrary band limited signals (for testing purposes)