Integration tests

[cedvdb]

I believe it's time we introduce automated integration testing as the lack of automated regression testing means issues can resurface.

For example there is a fix that's being merged for the payment element #2372 that's been merged lately, yet there is no test guaranteeing that 1. it works and 2. it does not break again in the future.

So I propose that we start with small ones that can be widened with time. Since this uses native views, a library like patrol (or other) can be used.

[remonh87]

Yeah it is a long wish to improve integration tests it is just we lack currently capacity to work on it.