[WIP] Add ExampleTests

#11: Adding tests for the core Example class.

(Not ready to merge yet.)

When testing the behaviour of `Example.name` I found that it only included the immediate parent group's name, rather than all nested parents like I expected. I've made the change, but if it turns out that was the expected behaviour I'm happy to revert it.
Ah of course! :facepalm:

If the test only creates a single example group, then by definition it's the root example group, so...I know exactly what behaviour to test for now :)