Parallelize PR system tests via GitHub Actions matrix.

.github/workflows/system-tests-latest-components.yml

@@ -168,11 +168,19 @@ jobs:
           } >> "$GITHUB_STEP_SUMMARY"
 
   run-system-tests:
-    name: Trigger system tests
+    name: Trigger system tests (shard ${{ matrix.shard }})
     needs: gather-refs
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - shard: 1
+            suites: release_test_shard_1
+          - shard: 2
+            suites: release_test_shard_2
     uses: precice/tutorials/.github/workflows/run_testsuite_workflow.yml@develop
     with:
-      suites: ${{ inputs.suites || 'release_test' }}
+      suites: ${{ matrix.suites }}
       build_args: "PLATFORM:ubuntu_2404,\
         PRECICE_REF:${{ needs.gather-refs.outputs.ref-precice }},\
         PYTHON_BINDINGS_REF:${{ needs.gather-refs.outputs.ref-python-bindings }},\

changelog-entries/829.md

@@ -0,0 +1 @@
+- Parallelized pull-request system tests via a GitHub Actions matrix over `release_test_shard_1` and `release_test_shard_2` [#829](https://github.com/precice/tutorials/pull/829)

tools/tests/README.md

@@ -54,6 +54,13 @@ To be able to fill in the right case tuple into the `tests.yaml`, you can use th
 
 ## Running the system tests on GitHub Actions
 
+The scheduled [System tests (latest components)](https://github.com/precice/tutorials/actions/workflows/system-tests-latest-components.yml)
+workflow runs as a GitHub Actions matrix over `release_test_shard_1` and `release_test_shard_2`
+(together they cover the same cases as `release_test`). When a shard fails, re-run only the
+failed matrix job. With multiple `precice-tests-vm` runners, shards may execute concurrently
+and may rebuild the same component images; we have not seen Docker build conflicts in local
+runs, but we can limit parallel jobs or add a shared build step if CI shows issues.
+
 Go to Actions > [Run Testsuite (manual)](https://github.com/precice/tutorials/actions/workflows/run_testsuite_manual.yml) to see this workflow.
 
 After bringing these changes to `master`, the manual triggering option should be visible on the top right. Until that happens, we can only trigger this workflow manually from the [GitHub CLI](https://github.blog/changelog/2021-04-15-github-cli-1-9-enables-you-to-work-with-github-actions-from-your-terminal/):

tools/tests/systemtests/TestSuite.py

@@ -33,6 +33,15 @@ class TestSuites(list):
     def __init__(self, testsuites: List[TestSuite]):
         self.testsuites = testsuites
 
+    @staticmethod
+    def _iter_tutorial_cases(tutorials_section):
+        """Yield tutorial case dicts, flattening YAML list aliases (e.g. shard lists)."""
+        for item in tutorials_section:
+            if isinstance(item, list):
+                yield from TestSuites._iter_tutorial_cases(item)
+            else:
+                yield item
+
     @classmethod
     def from_yaml(cls, path, parsed_tutorials: Tutorials):
         """
@@ -55,7 +64,8 @@ def from_yaml(cls, path, parsed_tutorials: Tutorials):
                 max_time_windows_of_tutorial = {}
                 timeouts_of_tutorial = {}
                 # iterate over tutorials:
-                for tutorial_case in test_suites_raw[test_suite_name]['tutorials']:
+                for tutorial_case in cls._iter_tutorial_cases(
+                        test_suites_raw[test_suite_name]['tutorials']):
                     tutorial = parsed_tutorials.get_by_path(tutorial_case['path'])
                     if not tutorial:
                         raise Exception(f"No tutorial with path {tutorial_case['path']} found.")

tools/tests/tests.yaml

@@ -500,8 +500,9 @@ test_suites:
 #####################################################################
 ## Test suites referring to the test suites defined above
 
-  release_test:
-    tutorials:
+  # Shards of release_test for parallel CI. release_test is their union (YAML anchors).
+  release_test_shard_1:
+    tutorials: &release_test_shard_1_tutorials
       - *breaking-dam-2d_fluid-openfoam_solid-calculix
       - *channel-transport_fluid-openfoam_transport-nutils
       - *channel-transport-reaction_fluid-fenics_chemical-fenics
@@ -526,6 +527,9 @@ test_suites:
       - *oscillator_mass-left-fmi_mass-right-fmi
       - *oscillator_mass-left-python_mass-right-python
       - *oscillator-overlap_mass-left-python_mass-right-python
+
+  release_test_shard_2:
+    tutorials: &release_test_shard_2_tutorials
       - *partitioned-backwards-facing-step_fluid1-openfoam_fluid2-openfoam
       - *partitioned-elastic-beam_dirichlet-calculix_neumann-calculix
       - *partitioned-heat-conduction_dirichlet-fenics_neumann-fenics
@@ -551,6 +555,11 @@ test_suites:
       - *water-hammer_fluid1d-left-nutils_fluid3d-right-openfoam
       - *wolf-sheep-soil-creep_soil-creep-landlab_wolf-sheep-grass-mesa
 
+  release_test:
+    tutorials:
+      - *release_test_shard_1_tutorials
+      - *release_test_shard_2_tutorials
+
   # These test suites take longer to run. They are available, but not regularly executed.
   extra:
     tutorials: