Running tests

Single test file (preferred during development)

Run one file directly against the local package:

JULIA_JUSTRELAX_BACKEND=CPU julia --project=test --startup-file=no test/test_shearband2D.jl

• JULIA_JUSTRELAX_BACKEND must be set (CPU, CUDA, or AMDGPU) — test files read ENV["JULIA_JUSTRELAX_BACKEND"] at the top and will throw a KeyError without it.
• Test files do push!(LOAD_PATH, ".."), and test/runtests.jl does pushfirst!(LOAD_PATH, dirname(@__DIR__)), so tests always run against the local checkout.
• The test environment is test/Project.toml, which holds the test-only packages (ParallelTestRunner, Suppressor, ExactFieldSolutions, ...) and dev's the local checkout. --project=. does not provide them, so run tests from --project=test or through Pkg.test.

Full suite

JULIA_JUSTRELAX_BACKEND=CPU julia --project=test --startup-file=no test/runtests.jl  # CPU
julia --project=. -e 'using Pkg; Pkg.test()'                            # CPU, via Pkg
julia --project=. -e 'using Pkg; Pkg.test(test_args=["--backend=CUDA"])' # GPU (adds CUDA via Pkg)

How test/runtests.jl works:

• Only files named test_*.jl are collected. deprecated_*.jl files are skipped.
• Non-MPI tests run in parallel via ParallelTestRunner; a worker is spawned per test except for a hardcoded list of light tests (traits, types, conversions, mask, mini kernels, interpolations, boundary conditions, JustPIC interface) that run without a worker.
• Files with MPI in the name (test_*_MPI.jl) are split out and run sequentially with mpiexec -n 2.
• You can filter: Pkg.test(test_args=["test_diffusion2D"]) runs only matching tests (burstedde and VanKeken are excluded when filtering).

Practical guidance

• The full suite is slow (solver tests run actual pseudo-transient iterations). Prefer one targeted test file. Quick smoke tests: test_types, test_traits, test_arrays_conversions, test_boundary_conditions2D (seconds, no solver). Physics regressions: test_shearband2D, test_diffusion2D, test_Blankenbach.
• MPI tests locally: mpiexec -n 2 julia --project=test --startup-file=no test/test_diffusion2D_multiphase_MPI.jl (use the MPI.jl-provided mpiexecjl if no system MPI is configured).
• GPU backends cannot be tested on this machine; CPU-pass + CI (CSCS GH200 pipeline in ci/cscs-gh200.yml runs CUDA + MPI tests) is the verification path.