Bug #16281: Update the test suite for Buster
Fix tests for mat with mat2
Our testsuite is using mat, that was repalced with mat2 and the commandline interface was changed to:
mat --show <file>.png
it creates a
<file>.cleaned.png if run with:
Test suite: update MAT test case for MAT2 (Closes: #16623).
Adjust to MAT2's CLI being significantly different from MAT v1's:
- The --check operation has been replaced by --show.
- The cleaned file is now saved under a different file name by default.
- Output is phrased differently.