TEST: added more tests for process_segmentation
TEST: added more tests for process_segmentation

Former-commit-id: a4259b3eed7328383e6194e2b2778f84d0fdbd0e [formerly dcace6cf40b40c0f948e3bef9fc92ec50bf5133d]
Former-commit-id: beb6617fdb7a93b567b1fc1039a06d18eba0be6b
Former-commit-id: 45e2f4b634026899953707a5ef28ee4baacb9e2c
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox