Branch 7.0 has failures that look legit on appveyor:

https://ci.appveyor.com/project/fabpot/symfony/builds/48330699?fullLog=true

Note that apppveyor tests Windows, but not only. There, we also test running the test suite without any extensions (e.g. to check that we added all @requires annotations in test, and we test on x86 (32-bit arch).