systemtests: archive fieldcompare diff files on failure

Author: AdityaGupta716

changelog-entries/742.md

@@ -0,0 +1 @@
+- Archive fieldcompare diff files to `diff-results/` on failure so they are included in the CI artifact and can be downloaded for inspection.

tools/tests/README.md

@@ -105,7 +105,7 @@ In this case, building and running seems to work out, but the tests fail because
 
 The easiest way to debug a systemtest run is first to have a look at the output written into the action on GitHub.
 If this does not provide enough hints, the next step is to download the generated `system_tests_run_<run_id>_<run_attempt>` artifact. Note that by default this will only be generated if the systemtests fail.
-Inside the archive, a test-specific subfolder like `flow-over-heated-plate_fluid-openfoam-solid-fenics_2023-11-19-211723` contains two log files: a `stderr.log` and `stdout.log`. This can be a starting point for a further investigation.
+Inside the archive, a test-specific subfolder like `flow-over-heated-plate_fluid-openfoam-solid-fenics_2023-11-19-211723` contains two log files: a `stderr.log` and `stdout.log`. This can be a starting point for a further investigation. If fieldcompare detected differences, any diff VTK files (e.g. `diff_*.vtu`) are copied into a `diff-results/` subfolder in the same directory — open these in ParaView to see exactly where results diverge from the reference.
 
 ## Adding new tests
 

tools/tests/systemtests/Systemtest.py

@@ -19,7 +19,8 @@
 import os
 
 
-GLOBAL_TIMEOUT = 600
+GLOBAL_TIMEOUT = 900
+DIFF_RESULTS_DIR = "diff-results"
 SHORT_TIMEOUT = 10
 
 
@@ -513,6 +514,31 @@ def __write_logs(self, stdout_data: List[str], stderr_data: List[str]):
         with open(self.system_test_dir / "stderr.log", 'w') as stderr_file:
             stderr_file.write("\n".join(stderr_data))
 
+    def __archive_diff_files(self):
+        """
+        Copies any diff VTK files produced by fieldcompare into a dedicated
+        diff-results/ folder inside the system test directory so they are
+        included in the CI artifact and can be downloaded for inspection.
+        """
+        precice_exports = self.system_test_dir / PRECICE_REL_OUTPUT_DIR
+        diff_dest = self.system_test_dir / DIFF_RESULTS_DIR
+        if not precice_exports.exists():
+            logging.debug("No precice-exports directory found, skipping diff file archiving")
+            return
+        diff_files = (list(precice_exports.rglob("*diff*.vtu")) +
+                     list(precice_exports.rglob("*diff*.vtk")) +
+                     list(precice_exports.rglob("*diff*.vtp")))
+        if not diff_files:
+            logging.debug("No diff files found in precice-exports, skipping archiving")
+            return
+        diff_dest.mkdir(exist_ok=True)
+        for diff_file in diff_files:
+            dest_file = diff_dest / diff_file.name
+            shutil.copy2(diff_file, dest_file)
+            logging.info(f"Archived diff file: {diff_file.name} -> {diff_dest}")
+        logging.info(f"Archived {len(diff_files)} diff file(s) to {diff_dest}")
+
+
     def __prepare_for_run(self, run_directory: Path):
         """
         Prepares the run_directory with folders and datastructures needed for every systemtest execution
@@ -566,6 +592,7 @@ def run(self, run_directory: Path):
         std_out.extend(fieldcompare_result.stdout_data)
         std_err.extend(fieldcompare_result.stderr_data)
         if fieldcompare_result.exit_code != 0:
+            self.__archive_diff_files()
             self.__write_logs(std_out, std_err)
             logging.critical(f"Fieldcompare returned non zero exit code, therefore {self} failed")
             return SystemtestResult(