Use compile-testing to improve testing

It might be a good idea to use the newly available compile-testing API (https://github.com/google/compile-testing) to improve the testing of the generated assertions. It can test that the generated assertions compile as well as doing a compile-tree diff of the generated file (instead of a plain-text diff).

That might be interesting indeed, right now I'm using assertj-examples for that.