Initial version of MigrationOptimizer and tests

tests/migrations/test_optimizer.py

@@ -0,0 +1,95 @@
+# encoding: utf8
+import operator
+from django.test import TestCase
+from django.db.migrations.optimizer import MigrationOptimizer
+from django.db import migrations
+from django.db import models
+
+
+class OptimizerTests(TestCase):
+    """
+    Tests the migration autodetector.
+    """
+
+    def optimize(self, operations):
+        """
+        Handy shortcut for getting results + number of loops
+        """
+        optimizer = MigrationOptimizer()
+        return optimizer.optimize(operations), optimizer._iterations
+
+    def assertOptimizesTo(self, operations, expected, exact=None, less_than=None):
+        result, iterations = self.optimize(operations)
+        self.assertEqual(expected, result)
+        if exact is not None and iterations != exact:
+            raise self.failureException("Optimization did not take exactly %s iterations (it took %s)" % (exact, iterations))
+        if less_than is not None and iterations >= less_than:
+            raise self.failureException("Optimization did not take less than %s iterations (it took %s)" % (less_than, iterations))
+
+    def test_operation_equality(self):
+        """
+        Tests the equality operator on lists of operations.
+        If this is broken, then the optimizer will get stuck in an
+        infinite loop, so it's kind of important.
+        """
+        self.assertEqual(
+            [migrations.DeleteModel("Test")],
+            [migrations.DeleteModel("Test")],
+        )
+        self.assertEqual(
+            [migrations.CreateModel("Test", [("name", models.CharField(max_length=255))])],
+            [migrations.CreateModel("Test", [("name", models.CharField(max_length=255))])],
+        )
+        self.assertNotEqual(
+            [migrations.CreateModel("Test", [("name", models.CharField(max_length=255))])],
+            [migrations.CreateModel("Test", [("name", models.CharField(max_length=100))])],
+        )
+        self.assertEqual(
+            [migrations.AddField("Test", "name", models.CharField(max_length=255))],
+            [migrations.AddField("Test", "name", models.CharField(max_length=255))],
+        )
+        self.assertNotEqual(
+            [migrations.AddField("Test", "name", models.CharField(max_length=255))],
+            [migrations.AddField("Test", "name", models.CharField(max_length=100))],
+        )
+        self.assertNotEqual(
+            [migrations.AddField("Test", "name", models.CharField(max_length=255))],
+            [migrations.AlterField("Test", "name", models.CharField(max_length=255))],
+        )
+
+    def test_single(self):
+        """
+        Tests that the optimizer does nothing on a single operation,
+        and that it does it in just one pass.
+        """
+        self.assertOptimizesTo(
+            [migrations.DeleteModel("Foo")],
+            [migrations.DeleteModel("Foo")],
+            exact = 1,
+        )
+
+    def test_create_delete_model(self):
+        """
+        CreateModel and DeleteModel should collapse into nothing.
+        """
+        self.assertOptimizesTo(
+            [
+                migrations.CreateModel("Foo", [("name", models.CharField(max_length=255))]),
+                migrations.DeleteModel("Foo"),
+            ],
+            [],
+        )
+
+    def test_create_alter_delete_model(self):
+        """
+        CreateModel, AlterModelTable, AlterUniqueTogether, and DeleteModel should collapse into nothing.
+        """
+        self.assertOptimizesTo(
+            [
+                migrations.CreateModel("Foo", [("name", models.CharField(max_length=255))]),
+                migrations.AlterModelTable("Foo", "woohoo"),
+                migrations.AlterUniqueTogether("Foo", [["a", "b"]]),
+                migrations.DeleteModel("Foo"),
+            ],
+            [],
+        )