Refactored 'test_physics_interface.py'.
Refactored 'test_physics_interface.py'.

daviddeng/azrael,olitheolix/azrael,daviddeng/azrael,daviddeng/azrael,olitheolix/azrael,olitheolix/azrael,olitheolix/azrael,daviddeng/azrael,olitheolix/azrael,daviddeng/azrael