fixing bug with dropping tables in auto migrations, and added test

Author: dantownsend

piccolo/apps/migrations/auto/schema_differ.py

@@ -241,7 +241,7 @@ def drop_tables(self) -> AlterStatements:
 
         return AlterStatements(
             statements=[
-                f"manager.drop_table(tablename='{i.tablename}')"
+                f"manager.drop_table(class_name='{i.class_name}', tablename='{i.tablename}')"  # noqa
                 for i in drop_tables
             ]
         )

tests/apps/migrations/auto/test_schema_differ.py

@@ -20,7 +20,19 @@ def test_drop_table(self):
         """
         Test dropping an existing table.
         """
-        pass
+        schema: t.List[DiffableTable] = []
+        schema_snapshot: t.List[DiffableTable] = [
+            DiffableTable(class_name="Band", tablename="band", columns=[])
+        ]
+        schema_differ = SchemaDiffer(
+            schema=schema, schema_snapshot=schema_snapshot, auto_input="y"
+        )
+
+        self.assertTrue(len(schema_differ.drop_tables.statements) == 1)
+        self.assertEqual(
+            schema_differ.drop_tables.statements[0],
+            "manager.drop_table(class_name='Band', tablename='band')",
+        )
 
     def test_rename_table(self):
         """