Increase Test Coverage

[marvin-hansen]

Currently, the core library is reasonable tested but some gaps exists.

The easiest way to get started:

1. Check the code coverage report:
   https://app.codecov.io/gh/deepcausality-rs/deep_causality

2. See where some gaps are

3. Look at the existing tests. Most are easy to copy & modify.
   https://github.com/deepcausality-rs/deep_causality/tree/main/deep_causality/tests

4. Add some new tests. Make sure you run make test & make check before before opening a PR.
   See details for make in the BUILD document.

5. Make a PR and wait for review

[MeenuyD]

Hello @marvin-hansen I would like to work on this issue can you please assign it to me?

[marvin-hansen]

Absolutely! Thank you @MeenuyD

[marvin-hansen]

@MeenuyD Make sure you read the build doc before you get started coding because it contains all the infos about the make automation scripts.

Thank you for your contribution.

[marvin-hansen]

And here is the link: https://github.com/deepcausality-rs/deep_causality/blob/main/BUILD.md