Refactor tests using `traits`

[dougb]

@colindean made some good suggestions in #14 around refactoring tests using traits (See comment) I tried to create a few new utility functions in #13, but I'd like to see if we can do something like Colin suggested, and make a pass through the tests and use any new traits or functions to make them more concise. I suspect we can reduce the duplicate code in the tests, greatly reduce the test SLOC and make it easier to develop tests.