Start adding operations that work and tests for them

tests/migrations/test_loader.py

@@ -1,11 +1,12 @@
-from django.test import TestCase
+from django.test import TestCase, TransactionTestCase
 from django.db import connection
+from django.db.migrations.loader import MigrationLoader
 from django.db.migrations.recorder import MigrationRecorder
 
 
 class RecorderTests(TestCase):
     """
-    Tests the disk and database loader.
+    Tests recording migrations as applied or not.
     """
 
     def test_apply(self):
@@ -27,3 +28,37 @@ class RecorderTests(TestCase):
             recorder.applied_migrations(),
             set(),
         )
+
+
+class LoaderTests(TransactionTestCase):
+    """
+    Tests the disk and database loader, and running through migrations
+    in memory.
+    """
+
+    def test_load(self):
+        """
+        Makes sure the loader can load the migrations for the test apps,
+        and then render them out to a new AppCache.
+        """
+        # Load and test the plan
+        migration_loader = MigrationLoader(connection)
+        self.assertEqual(
+            migration_loader.graph.forwards_plan(("migrations", "0002_second")),
+            [("migrations", "0001_initial"), ("migrations", "0002_second")],
+        )
+        # Now render it out!
+        project_state = migration_loader.graph.project_state(("migrations", "0002_second"))
+        self.assertEqual(len(project_state.models), 2)
+
+        author_state = project_state.models["migrations", "author"]
+        self.assertEqual(
+            [x for x, y in author_state.fields],
+            ["id", "name", "slug", "age", "important"]
+        )
+
+        book_state = project_state.models["migrations", "book"]
+        self.assertEqual(
+            [x for x, y in book_state.fields],
+            ["id", "author"]
+        )