Simple tests:

python test_python.py       # Test to see that Python runs at all.
python test_openmm.py       # Test that the system can find a working platform
python test_cuda.py         # Test to see if the system has a CUDA enabled GPU

More involved tests (seconds):

python test_systems.py      # Test that a number of test systems give the expected energies on Reference platform.

Time-consuming tests (minutes):

python test_platforms.py    # Test that non-Reference platforms produce energies close to Reference platform on all test systems.
python test_optimize.py     # Test that all optimizers work with all test systems in all platforms.
python test_thermostats.py  # Test that all thermostats give equivalent results for a few test systems.