Code coverage is fairly low

[pmeier]

Although the coverage is 78%, the tests cover very little apart from the regular cases. A lot of if branches especially in error cases are not covered. Additionally, the following functions and modules are not covered at all:

• unlocknn.metrics
• unlocknn.megnet_utils
  • .default_megnet_config()
  • .scale_targets()

[a-ws-m]

I've added the following changes:

• Some tests to ensure the metrics values match expectations for some "toy" data.
• Some tests for thawing/freezing layers, which I think had a lot of branches.
• A test for create_megnet_input(), which wraps scale_targets() (it felt redundant to test a one-liner that only appears once, so I thought it'd be beneficial to ensure the wrapping function works as expected).

I think default_megnet_config() doesn't require a test. It comes from the authors of MEGNet and essentially works to abstract a very common combination of keyword arguments into a one-liner. Because of the nature of the function (essentially, it's a parameterizable dictionary) I can't think of a useful test to be run.