Investigate poor unit test performance

[delcypher]

With different versions of mono the time taken to execute the unit tests seems to have significantly regressed.

Mono 4.4.1

Tests run: 256, Errors: 0, Failures: 0, Inconclusive: 0, Time: 173.8809436 seconds
  Not run: 14, Invalid: 0, Ignored: 14, Skipped: 0

Mono 3.4.0

Tests run: 256, Errors: 0, Failures: 0, Inconclusive: 0, Time: 7.9253886 seconds
  Not run: 14, Invalid: 0, Ignored: 14, Skipped: 0