Add first few tests. Starting with helpers

I am not sure what your plans are with the tests but I took the freedom to start implementing the first few.

I assumed you wouldn't have like third party libraries so I just tried to stick with an idiomatic way of doing things, taking examples from here and there. Some of those tests are silly and, of course, there still a lot of work but we should always start somewhere.

I haven't spend that much time on those to I won't take it personally if this is dismissed ;) However, if you prefer using something else, if you want a slightly different style, etc... I would be happy to change the code. And if it's working out, pushing the coverage a little bit.