Revisit pipeline and element tests

[mat-hek]

Some tests for pipeline and element are a bit outdated. They should be revisited and Espec ones should be rewritten to ExUnit.

We should consider adding a code coverage tool as well

[mat-hek]

Partially done by #203

[djanda97]

Searching for use Espec in this repo resulted in 0 matches. Does this mean that all tests were converted to ExUnit and this issue can be closed?

[mat-hek]

Yes, they were all converted, thanks