Integrate IGNORE into cache

tests/functional/test_cache.py

@@ -28,7 +28,6 @@ else:
     import mock
 
 
-
 class CacheTest(unittest.TestCase):
     MIGRATION_FILE = os.path.join(fixtures.ALTER_COLUMN_PROJECT, 'test_app', 'migrations', '0001_initial.py')
     fd, temp_path = tempfile.mkstemp()
@@ -73,7 +72,30 @@ class CacheTest(unittest.TestCase):
         self.assertTrue(linter.has_errors)
 
     def test_cache_ignored(self):
-        pass
+        cache_file = os.path.join(DEFAULT_CACHE_PATH, 'test_project_ignore_migration.pickle')
+        if os.path.exists(cache_file):
+            os.remove(cache_file)
+        linter = MigrationLinter(fixtures.IGNORE_MIGRATION_PROJECT)
+
+        with mock.patch.object(MigrationLinter, 'get_sql', wraps=linter.get_sql)as sql_mock:
+            linter.lint_all_migrations()
+            sql_mock.assert_called()
+
+        cache = Cache(
+            fixtures.IGNORE_MIGRATION_PROJECT,
+            DEFAULT_CACHE_PATH
+        )
+        cache.load()
+
+        self.assertEqual(cache['63230606af0eccaef7f1f78c537c624c']['result'], 'OK')
+        self.assertEqual(cache['5c5ca1780a9f28439c1defc1f32af894']['result'], 'IGNORE')
+
+        # Start the Linter again -> should use cache now.
+        linter = MigrationLinter(fixtures.IGNORE_MIGRATION_PROJECT)
+
+        with mock.patch.object(MigrationLinter, 'get_sql', wraps=linter.get_sql)as sql_mock:
+            linter.lint_all_migrations()
+            sql_mock.assert_not_called()
 
     def test_cache_modified(self):
         cache_file = os.path.join(DEFAULT_CACHE_PATH, 'test_project_alter_column.pickle')