test: add MigrationsTestCase to verify forward and backward migrations (#477)

Agent-Logs-Url: https://github.com/fabiocaccamo/django-admin-interface/sessions/2fa3d623-bdd8-4737-93ba-94c0965cbc3b

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: fabiocaccamo <1035294+fabiocaccamo@users.noreply.github.com>

Author: Copilot

tests/test_migrations.py

@@ -0,0 +1,29 @@
+from django.core.management import call_command
+from django.db.migrations.exceptions import IrreversibleError
+from django.test import TransactionTestCase
+
+
+class MigrationsTestCase(TransactionTestCase):
+    """
+    Generic test case that verifies all migrations for a given app can be
+    applied forward and reversed (to zero) without errors.
+
+    Reusable in other projects: just subclass and set ``app_label``.
+    """
+
+    app_label = "admin_interface"
+
+    def tearDown(self):
+        # Restore migrations to the latest state even if the test fails
+        # so that subsequent tests find the DB in the expected state.
+        call_command("migrate", self.app_label, verbosity=0)
+        super().tearDown()
+
+    def test_migrate_forward_and_backward(self):
+        try:
+            call_command("migrate", self.app_label, "zero", verbosity=0)
+        except IrreversibleError as e:
+            self.fail(
+                f"Migrations for '{self.app_label}' are not fully reversible: {e}"
+            )
+        call_command("migrate", self.app_label, verbosity=0)