Test suite

python3 tests/run_tests.py

The suite runs short calculations and checks them against things that must be true, rather than against stored output. A golden-file test tells you that something changed. These tell you whether the answer is right.

Test	Checks
`virial`	A relaxed \(n=1.5\) polytrope satisfies \(W = -\frac{3}{5-n}\frac{GM^2}{R}\), and \(U = -W/2\).
`energy`	Total energy is conserved through the run.
`quiet`	A relaxed star stays put: kinetic energy remains negligible.
`ranks`	The answer does not depend on how many MPI ranks are used.
`cpu_gpu`	The CPU and GPU builds agree.
`guard_ngravprocs`	Asking for more gravity processes than there are GPUs is clamped rather than fatal.
`startfiles`	Bodies are read from the file names given in `sph.input`, not from names compiled into the code.
`periodic`	A fully periodic box conserves momentum to round-off and energy closely, keeps every particle inside the box, and shows no density seam at its faces.
`periodic_block`	Block timesteps in a periodic box, with a hot half on shorter steps, give the same densities as shared timesteps to within 1% and keep every particle inside the box.
`guard_periodic`	A periodic box too small for the kernel (2h beyond half a period) stops the run with a message rather than missing neighbours.

Options:

python3 tests/run_tests.py --list            # what exists
python3 tests/run_tests.py virial energy     # named tests only
python3 tests/run_tests.py --np 2            # fewer ranks
python3 tests/run_tests.py --exe /path/to/..._sph   # skip the build
python3 tests/run_tests.py --with-cpu        # also build the CPU version
python3 tests/run_tests.py --quick           # smaller star, same assertions

Each build happens in a copy of the source under the suite’s own scratch directory, so a test run leaves the repository untouched.

Adding a test

Write a function taking a context and returning a one-line description of what it verified, raise Fail with the numbers when it does not hold, and add it to the TESTS dictionary in tests/run_tests.py. Prefer an invariant that has to be true over a value that happened to be produced.