Integration tests - false positives when the output file is not modified

[ramonacat]

Problem
When an integration test that produces an output file is ran, it might give a false positive, if the run does not change the file and previous run was succesful.

Steps

1. Run an integration tests that outputs to a file
2. Change the filename that the test outputs to (without changing assertions)
3. Run the test again - it will pass, though it should fail

Possible Solution(s)
Remove the output files that are used in assertions before running tests?

Notes

Output of rustup --version:
Output of rustup show:
Output of tremor --version: