Add the start of some operation tests

tests/migrations/test_operations.py

@@ -0,0 +1,84 @@
+from django.test import TransactionTestCase
+from django.db import connection, models, migrations
+from django.db.migrations.state import ProjectState, ModelState
+
+
+class OperationTests(TransactionTestCase):
+    """
+    Tests running the operations and making sure they do what they say they do.
+    Each test looks at their state changing, and then their database operation -
+    both forwards and backwards.
+    """
+
+    def assertTableExists(self, table):
+        self.assertIn(table, connection.introspection.get_table_list(connection.cursor()))
+
+    def assertTableNotExists(self, table):
+        self.assertNotIn(table, connection.introspection.get_table_list(connection.cursor()))
+
+    def set_up_test_model(self, app_label):
+        """
+        Creates a test model state and database table.
+        """
+        # Make the "current" state
+        creation = migrations.CreateModel(
+            "Pony",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("pink", models.BooleanField(default=True)),
+            ],
+        )
+        project_state = ProjectState()
+        creation.state_forwards(app_label, project_state)
+        # Set up the database
+        with connection.schema_editor() as editor:
+            creation.database_forwards(app_label, editor, ProjectState(), project_state)
+        return project_state
+
+    def test_create_model(self):
+        """
+        Tests the CreateModel operation.
+        Most other tests use this as part of setup, so check failures here first.
+        """
+        operation = migrations.CreateModel(
+            "Pony",
+            [
+                ("id", models.AutoField(primary_key=True)),
+                ("pink", models.BooleanField(default=True)),
+            ],
+        )
+        # Test the state alteration
+        project_state = ProjectState()
+        new_state = project_state.clone()
+        operation.state_forwards("test_crmo", new_state)
+        self.assertEqual(new_state.models["test_crmo", "pony"].name, "Pony")
+        self.assertEqual(len(new_state.models["test_crmo", "pony"].fields), 2)
+        # Test the database alteration
+        self.assertTableNotExists("test_crmo_pony")
+        with connection.schema_editor() as editor:
+            operation.database_forwards("test_crmo", editor, project_state, new_state)
+        self.assertTableExists("test_crmo_pony")
+        # And test reversal
+        with connection.schema_editor() as editor:
+            operation.database_backwards("test_crmo", editor, new_state, project_state)
+        self.assertTableNotExists("test_crmo_pony")
+
+    def test_delete_model(self):
+        """
+        Tests the DeleteModel operation.
+        """
+        project_state = self.set_up_test_model("test_dlmo")
+        # Test the state alteration
+        operation = migrations.DeleteModel("Pony")
+        new_state = project_state.clone()
+        operation.state_forwards("test_dlmo", new_state)
+        self.assertNotIn(("test_dlmo", "pony"), new_state.models)
+        # Test the database alteration
+        self.assertTableExists("test_dlmo_pony")
+        with connection.schema_editor() as editor:
+            operation.database_forwards("test_dlmo", editor, project_state, new_state)
+        self.assertTableNotExists("test_dlmo_pony")
+        # And test reversal
+        with connection.schema_editor() as editor:
+            operation.database_backwards("test_dlmo", editor, new_state, project_state)
+        self.assertTableExists("test_dlmo_pony")