Move `tests/Testing` to Integration testing

[Aidan Casey]

Somewhere along the way the Testing directory got moved to the tests root. We need to do the following:

• Move that directory to the integration tests directory.
• Rename test_get_requests_failure to test_assert_ok_works.
• Remove the todo comment and replace exception expectation with a PHPunit assertion failed exception expectation.

[Aidan Casey]

Solved by #199.