Improved foundational backend unit tests (#1405)

* part one of adding tests, updating core

* Apply fixes from StyleCI

[ci skip] [skip ci]

* we need xdebug for code coverage, and hhvm was already removed

* forgot about the sidecar for mysql completely 🤦

* gitignore removed this installed json we need to fake that we have extensions

* using reguarded closure

tests/tmp/vendor/composer/installed.json

@@ -0,0 +1 @@
+{}