Support a local repository of regression test assets

tests/regression/conftest.py

@@ -0,0 +1,7 @@
+def pytest_addoption(parser):
+    parser.addoption(
+        "--local-repository",
+        action="store",
+        default=None,
+        help="Location of the local repository of reference MFiles.",
+    )

tests/regression/test_process_input_files.py

@@ -286,11 +286,15 @@ def test_input_file(
     opt_params_only: bool,
     hide_model_logs,
     cli_runner,
+    request,
 ):
     """Tests each input file in the 'input_files' directory.
 
-    The test will locate and download a remote reference MFile that was
-    generated by running the input file on the 'main' branch.
+    The test will locate a remote reference file:
+    * Normally, this is a file that was generated in the PROCESS CI by
+    running an input file on the main branch.
+    * If a `--local-repository` directory is provided, the reference file is found
+    in that directory.
 
     The input file will then be run locally and compared to the reference file.
     The test will fail if:
@@ -312,7 +316,7 @@ def test_input_file(
     :param reg_tolerance: user specified tolerance, percentage differences below which
     are ignored.
     :type reg_tolerance: float
-    :param opt_params_only: if True, user specificied that only optimisation parameters
+    :param opt_params_only: if True, user specified that only optimisation parameters
     should be compared in the test.
     :type opt_params_only: bool
     """
@@ -327,9 +331,25 @@ def test_input_file(
 
     scenario = RegressionTestScenario(new_input_file)
 
-    reference_mfile = tracked_regression_test_assets.get_reference_mfile(
-        scenario.scenario_name
-    )
+    local_repo = request.config.getoption("--local-repository")
+
+    if local_repo is None:
+        reference_mfile = tracked_regression_test_assets.get_reference_mfile(
+            scenario.scenario_name
+        )
+    else:
+        # Note that the MFILE must be present in the local repository with the exact
+        # naming pattern as the IN.DAT (including capitalisation, IN.DAT and MFILE.DAT
+        # must be capitals):
+        # - MY.IN.DAT -> MY.MFILE.DAT
+        # - MY_IN.DAT -> MY_MFILE.DAT
+        # - myIN.DAT -> myMFILE.DAT
+        # This naming convention is consistent with PROCESS but is inconsistent with the
+        # remote repository for legacy reasons (i.e. scenario_name does not follow
+        # this convention).
+        reference_mfile = Path(
+            local_repo, input_file.name.replace("IN.DAT", "MFILE.DAT")
+        )
 
     scenario.run(solver_name, cli_runner)