Add Tests

## What needs to happen?
Add a test directory and create at least one test file.

For examples, look at [timelapse-colorizer](https://github.com/allen-cell-animated/timelapse-colorizer/tree/main/tests) or [simularium-viewer](https://github.com/simularium/simularium-viewer/tree/main/src/test)

Ideas of tests we could have:
- unpacking nested firebase references
- anything that's in the /util folder
