Inconsistent behavior of frontend tests

[janniclas]

Describe the bug
Sometimes the angular tests executed with ng test on the travis build pipeline fail and upon rerunning the pipeline the tests are successful. This might be caused due to the random executing order of the test causing some unwanted behavior (which shouldn't be there in any case). This needs further investigation.

[Ayybeeshafi]

I figured out that failing of test is not random. Whichever test succeeded DashboardOverviewComponent should createtestcase it failed. We are using RouterModule in this testcase. I presume that this component couldn't be removed before next test or something like that.
My solution for this problem was calling
fixture.destroy() in afterEach in spec of DashboardOverviewComponent.
Tests are executing fine on the build pipeline as well as my machine.