Add coverage re #11114

arches/apps.py

@@ -12,7 +12,7 @@
 
 try:
     import tomllib  # Python 3.11+
-except ImportError:
+except ImportError:  # pragma: no cover
     # Python 3.10 depends on tomli instead
     import tomli as tomllib
 
@@ -93,13 +93,13 @@ def check_arches_compatibility(app_configs, **kwargs):
         except PackageNotFoundError:
             # Not installed by pip: read pyproject.toml directly
             toml_path = Path(config.path).parent / "pyproject.toml"
-            if not toml_path.exists():
+            if not toml_path.exists():  # pragma: no cover
                 raise ValueError
             with open(toml_path, "rb") as f:
                 data = tomllib.load(f)
                 try:
                     project_requirements = data["project"]["dependencies"]
-                except KeyError:
+                except KeyError:  # pragma: no cover
                     raise ValueError from None
         try:
             for requirement in project_requirements:

tests/utils/test_checks.py

@@ -0,0 +1,46 @@
+from importlib.metadata import PackageNotFoundError
+from unittest import mock
+
+from django.apps import apps
+from django.core.management import call_command
+from django.core.management.base import SystemCheckError
+from django.test import SimpleTestCase
+
+
+# these tests can be run from the command line via
+# python manage.py test tests.utils.test_checks.SystemCheckTests --settings="tests.test_settings"
+
+
+def raise_package_not_found_error(name):
+    raise PackageNotFoundError
+
+
+class SystemCheckTests(SimpleTestCase):
+    def test_compatibility(self):
+        """Patch core arches to be an "arches application" so we can check
+        its range of compatible arches version, which it won't have.
+        """
+
+        core_arches_appconfig = apps.get_app_config("arches")
+        core_arches_appconfig.is_arches_application = True
+        self.addCleanup(setattr, core_arches_appconfig, "is_arches_application", False)
+
+        # Test something pip-installed.
+        with self.assertRaisesMessage(
+            SystemCheckError, "Invalid or missing arches requirement"
+        ):
+            call_command("check")
+
+        # Mock having to go to the pyproject.toml
+        with mock.patch("arches.apps.requires", raise_package_not_found_error):
+            with self.assertRaisesMessage(
+                SystemCheckError, "Invalid or missing arches requirement"
+            ):
+                call_command("check")
+
+        # Mock an incompatible version requirement.
+        with mock.patch("arches.apps.requires", lambda app_name: ["arches==0.0.1"]):
+            with self.assertRaisesMessage(
+                SystemCheckError, "Incompatible arches requirement"
+            ):
+                call_command("check")