Add document signature setting migration test

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

mayan/apps/document_signatures/tests/test_setting_migrations.py

@@ -0,0 +1,35 @@
+from __future__ import unicode_literals
+
+from django.conf import settings
+from django.utils.encoding import force_bytes
+
+from mayan.apps.common.tests.base import BaseTestCase
+from mayan.apps.common.tests.mixins import EnvironmentTestCaseMixin
+from mayan.apps.smart_settings.classes import Setting
+from mayan.apps.storage.utils import NamedTemporaryFile
+
+from ..settings import setting_storage_backend_arguments
+
+
+class SourceSettingMigrationTestCase(EnvironmentTestCaseMixin, BaseTestCase):
+    def test_signatures_storage_backend_arguments_0001_migration(self):
+
+        test_value = {'location': 'test value'}
+
+        with NamedTemporaryFile() as file_object:
+            settings.CONFIGURATION_FILEPATH = file_object.name
+            file_object.write(
+                force_bytes(
+                    '{}: {}'.format(
+                        'SIGNATURES_STORAGE_BACKEND_ARGUMENTS',
+                        '"{}"'.format(Setting.serialize_value(value=test_value))
+                    )
+                )
+            )
+            file_object.seek(0)
+            Setting._config_file_cache = None
+
+            self.assertEqual(
+                setting_storage_backend_arguments.value,
+                test_value
+            )