FBP Go: Unit tests

**Describe the task**
Put in place automated testing with sufficient coverage.

**Acceptance Criteria**
- [ ] Able to generate CFFDRS test Json.
- [ ] All tests run automated on code commits as Github actions.
- [ ] Anything that has come up in user feedback that has been added or modified is tested, eg.) BUI doesn't change with new fuel type selection.
- [ ] Testing what could potential break if another dev is working with the code, eg.) changing input range on a slider that would cause CFFDRS code to break or throw an exception due to out of range values.
- [ ] Pull requests are reviewed and approved by at least one (ideally all) devs going forward.

**Additional context**
- We are not following our best practice to have pull requests reviewed by other devs.
- FBP Go originated from an innovation sprint and needs to mature into a product that follows industry best practice and involves the entire team.

No files, tests, or entry points are named. Start by locating the FBP Go implementation, existing tests, and GitHub Actions workflows, then review the CFFDRS JSON generation and user-feedback cases; done means automated coverage and commit-time test execution are in place.

Written by the indexing model from the issue text.