Increase test coverage to 80% ⚡️

[JamieSlome]

The codebase currently has low test coverage. To ensure the stability of the library and speed up pull request reviews, the test coverage should be increased to a common standard of 80%.

Code coverage reports are currently being developed in #203.

### Tasks
- [ ] Create test files in `test` folder
- [ ] Run `nyc` to understand the current test score and code areas requiring more test coverage
- [ ] Ensure all files reported by `nyc` have at least 80% coverage on all code aspects (functions, lines, etc.)

[IshwaryaSriram]

Hi @JamieSlome, I would like to contribute to increasing test coverage.

[JamieSlome]

@IshwaryaSriram - all yours 🙌

[jescalada]

Closing this as we already have >80% coverage on main. 🎉