Clean up unit test output

[pprkut]

• Use a mocked logger to remove output spam
• Fix phpunit deprecation warnings

This should fix all the issues scrutinizer has with the unit tests.

[pprkut]

Well, boo :disappointed:

The OOM error remains, and I can't reproduce that one locally.

[pprkut]

However, it looks like the OOM isn't actually an issue and it's rather failing on this line:

The coverage file '/home/scrutinizer/build/coverage.xml' was not found.

because

Error:         No code coverage driver is available