Add some field schema alteration methods and tests.

tests/modeltests/schema/tests.py

@@ -2,8 +2,9 @@ from __future__ import absolute_import
 import copy
 import datetime
 from django.test import TestCase
-from django.db.models.loading import cache
 from django.db import connection, DatabaseError, IntegrityError
+from django.db.models.fields import IntegerField, TextField
+from django.db.models.loading import cache
 from .models import Author, Book
 
 
@@ -18,6 +19,8 @@ class SchemaTests(TestCase):
 
     models = [Author, Book]
 
+    # Utility functions
+
     def setUp(self):
         # Make sure we're in manual transaction mode
         connection.commit_unless_managed()
@@ -51,6 +54,18 @@ class SchemaTests(TestCase):
         cache.app_store = self.old_app_store
         cache._get_models_cache = {}
 
+    def column_classes(self, model):
+        cursor = connection.cursor()
+        return dict(
+            (d[0], (connection.introspection.get_field_type(d[1], d), d))
+            for d in connection.introspection.get_table_description(
+                cursor,
+                model._meta.db_table,
+            )
+        )
+
+    # Tests
+
     def test_creation_deletion(self):
         """
         Tries creating a model's table, and then deleting it.
@@ -100,3 +115,60 @@ class SchemaTests(TestCase):
                 pub_date = datetime.datetime.now(),
             )
             connection.commit()
+
+    def test_create_field(self):
+        """
+        Tests adding fields to models
+        """
+        # Create the table
+        editor = connection.schema_editor()
+        editor.start()
+        editor.create_model(Author)
+        editor.commit()
+        # Ensure there's no age field
+        columns = self.column_classes(Author)
+        self.assertNotIn("age", columns)
+        # Alter the name field to a TextField
+        new_field = IntegerField(null=True)
+        new_field.set_attributes_from_name("age")
+        editor = connection.schema_editor()
+        editor.start()
+        editor.create_field(
+            Author,
+            new_field,
+        )
+        editor.commit()
+        # Ensure the field is right afterwards
+        columns = self.column_classes(Author)
+        self.assertEqual(columns['age'][0], "IntegerField")
+        self.assertEqual(columns['age'][1][6], True)
+
+    def test_alter(self):
+        """
+        Tests simple altering of fields
+        """
+        # Create the table
+        editor = connection.schema_editor()
+        editor.start()
+        editor.create_model(Author)
+        editor.commit()
+        # Ensure the field is right to begin with
+        columns = self.column_classes(Author)
+        self.assertEqual(columns['name'][0], "CharField")
+        self.assertEqual(columns['name'][1][3], 255)
+        self.assertEqual(columns['name'][1][6], False)
+        # Alter the name field to a TextField
+        new_field = TextField(null=True)
+        new_field.set_attributes_from_name("name")
+        editor = connection.schema_editor()
+        editor.start()
+        editor.alter_field(
+            Author,
+            Author._meta.get_field_by_name("name")[0],
+            new_field,
+        )
+        editor.commit()
+        # Ensure the field is right afterwards
+        columns = self.column_classes(Author)
+        self.assertEqual(columns['name'][0], "TextField")
+        self.assertEqual(columns['name'][1][6], True)