1 files changed, 59 insertions, 0 deletions
diff --git a/tests/migrations/test_executor.py b/tests/migrations/test_executor.py
index 12bdabb172..32cdc5e09c 100644
--- a/tests/migrations/test_executor.py
+++ b/tests/migrations/test_executor.py
@@ -1,5 +1,6 @@
 from django.apps.registry import apps as global_apps
 from django.db import connection
+from django.db.migrations.exceptions import InvalidMigrationPlan
 from django.db.migrations.executor import MigrationExecutor
 from django.db.migrations.graph import MigrationGraph
 from django.db.migrations.recorder import MigrationRecorder
@@ -145,6 +146,64 @@ class ExecutorTests(MigrationTestBase):
         executor.recorder.record_unapplied("migrations", "0002_second")
         executor.recorder.record_unapplied("migrations", "0001_initial")
 
+    @override_settings(MIGRATION_MODULES={
+        "migrations": "migrations.test_migrations",
+        "migrations2": "migrations2.test_migrations_2_no_deps",
+    })
+    def test_mixed_plan_not_supported(self):
+        """
+        Although the MigrationExecutor interfaces allows for mixed migration
+        plans (combined forwards and backwards migrations) this is not
+        supported.
+        """
+        # Prepare for mixed plan
+        executor = MigrationExecutor(connection)
+        plan = executor.migration_plan([("migrations", "0002_second")])
+        self.assertEqual(
+            plan,
+            [
+                (executor.loader.graph.nodes["migrations", "0001_initial"], False),
+                (executor.loader.graph.nodes["migrations", "0002_second"], False),
+            ],
+        )
+        executor.migrate(None, plan)
+        # Rebuild the graph to reflect the new DB state
+        executor.loader.build_graph()
+        self.assertIn(('migrations', '0001_initial'), executor.loader.applied_migrations)
+        self.assertIn(('migrations', '0002_second'), executor.loader.applied_migrations)
+        self.assertNotIn(('migrations2', '0001_initial'), executor.loader.applied_migrations)
+
+        # Generate mixed plan
+        plan = executor.migration_plan([
+            ("migrations", None),
+            ("migrations2", "0001_initial"),
+        ])
+        msg = (
+            'Migration plans with both forwards and backwards migrations are '
+            'not supported. Please split your migration process into separate '
+            'plans of only forwards OR backwards migrations.'
+        )
+        with self.assertRaisesMessage(InvalidMigrationPlan, msg) as cm:
+            executor.migrate(None, plan)
+        self.assertEqual(
+            cm.exception.args[1],
+            [
+                (executor.loader.graph.nodes["migrations", "0002_second"], True),
+                (executor.loader.graph.nodes["migrations", "0001_initial"], True),
+                (executor.loader.graph.nodes["migrations2", "0001_initial"], False),
+            ],
+        )
+        # Rebuild the graph to reflect the new DB state
+        executor.loader.build_graph()
+        executor.migrate([
+            ("migrations", None),
+            ("migrations2", None),
+        ])
+        # Are the tables gone?
+        self.assertTableNotExists("migrations_author")
+        self.assertTableNotExists("migrations_book")
+        self.assertTableNotExists("migrations2_otherauthor")
+
     @override_settings(MIGRATION_MODULES={"migrations": "migrations.test_migrations"})
     def test_soft_apply(self):
         """