unit_testing: image: add more Slicer tests
unit_testing: image: add more Slicer tests


Former-commit-id: 5c1536c34a1ba98832563adf2eaed9e31f12f208
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox