Work in Progress: Add first tests

[ms14981]

This is my progress so far to beginning a unit test suite. One test will still fail until #71 is merged in.

Unfortunately, I keep getting a variety of errors and haven't managed to successfully get the following all working at the same time:

1. Running the tests.
2. Having the react package available to the demo and the root.
3. Preventing version clashes in both the root package and the demo.
4. Passing the build and license checks.

Hopefully this will be a good starting place for anyone who picks this up.

My previous attempts are: #65 #66 #67