TESTS!!!!

[lukesutton]

We only have minimal tests for the auto layout solver at present. Not great.

Thankfully, since most rendering is ultimately just updating a buffer, it's simple for us to perform isolated tests for everything, without worrying about having an actual terminal on hand.

One option — especially for the layouts — is to use a Quickcheck style library to derive a range of inputs. That's more likely to catch edge cases when compared to crafting specific tests.