Implement mass2d_triangle regression test using pytest
Modularize mass_vector_ffc demo
mass_vector_ffc demo: add option to return the result for testing
Implement mass_vector_ffc regression test using pytest
Modularize weak_bcs_ffc demo
weak_bcs_ffc demo: add option to return the result for testing
Implement weak_bcs_ffc regression test using pytest
Switch to pytest based regression tests