Get rid of unsafePerformIO

[marcellussiegburg]

Currently unsafePerformIO is used to perform tests.

I think the only reason for doing so is, because it was always done like this. However it is not required to do so. Commit 9ba7c0c fixes this.

But the change would involve updating the underlying GHC_PACKAGE_DB. That is why this change should happen probably after the semester has ended.

[marcellussiegburg]

It is possible that this change would also make the work-around of #9 unnecessary as there are several server-timeouts are already involved (but might simply not get accounted for because of unsafePerformIO)?