Optionally create a single app instance per test case class

docs/index.rst

@@ -121,6 +121,23 @@ a special ``json`` attribute appended to the ``Response`` object::
             response = self.client.get("/ajax/")
             self.assertEquals(response.json, dict(success=True))
 
+
+Single app instance
+-------------------
+
+In some cases, creating the app instance can be expensive. If you want to create one
+app instance per TestCase class, you can use the ``create_app_once`` flag. This works
+on both TestCase and LiveServerTestCase and is not enabled by default::
+
+    from flask_testing import TestCase
+
+    class MyTest(TestCase):
+        create_app_once = True
+
+        def test_something(self):
+            pass
+
+
 Opt to not render the templates
 -------------------------------
 

flask_testing/utils.py

@@ -57,7 +57,7 @@
 except ImportError:  # pragma: no cover
     _is_signals = False
 
-__all__ = ["TestCase"]
+__all__ = ('TestCase', 'LiveServerTestCase')
 
 
 class ContextVariableDoesNotExist(Exception):
@@ -110,7 +110,28 @@ def _check_for_signals_support():
         )
 
 
-class TestCase(unittest.TestCase):
+class SingletonAppMixin(object):
+    create_app_once = False
+    _app_instance = None
+
+    def _get_or_create_app(self):
+        """
+        This is a lazy way of doing class setup since we want to be consistent
+        and not have users call super in setUpClass if they do not call it in
+        setUp. Returns the singleton app if the test case has specified using
+        a single app.
+        """
+        cls = self.__class__
+        if not cls.create_app_once:
+            return self.create_app()
+
+        if not cls._app_instance:
+            cls._app_instance = self.create_app()
+
+        return cls._app_instance
+
+
+class TestCase(unittest.TestCase, SingletonAppMixin):
     render_templates = True
     run_gc_after_test = False
 
@@ -141,7 +162,7 @@ def debug(self):
             self._post_teardown()
 
     def _pre_setup(self):
-        self.app = self.create_app()
+        self.app = self._get_or_create_app()
 
         self._orig_response_class = self.app.response_class
         self.app.response_class = _make_test_response(self.app.response_class)
@@ -410,8 +431,8 @@ def assert500(self, response, message=None):
 
 # A LiveServerTestCase useful with Selenium or headless browsers
 # Inspired by https://docs.djangoproject.com/en/dev/topics/testing/#django.test.LiveServerTestCase
+class LiveServerTestCase(unittest.TestCase, SingletonAppMixin):
 
-class LiveServerTestCase(unittest.TestCase):
     def create_app(self):
         """
         Create your Flask app here, with any
@@ -426,7 +447,7 @@ def __call__(self, result=None):
         """
 
         # Get the app
-        self.app = self.create_app()
+        self.app = self._get_or_create_app()
 
         self._configured_port = self.app.config.get('LIVESERVER_PORT', 5000)
         self._port_value = multiprocessing.Value('i', self._configured_port)

tests/__init__.py

@@ -4,18 +4,20 @@
 
 from .test_twill import TestTwill, TestTwillDeprecated
 from .test_utils import TestSetup, TestSetupFailure, TestClientUtils, \
-        TestLiveServer, TestTeardownGraceful, TestRenderTemplates, \
-        TestNotRenderTemplates, TestRestoreTheRealRender, \
-        TestLiveServerOSPicksPort
+     TestLiveServer, TestTeardownGraceful, TestRenderTemplates, \
+     TestNotRenderTemplates, TestRestoreTheRealRender, TestSingletonApp, \
+     TestLiveServerOSPicksPort, TestLiveServerSingletonApp
 
 
 def suite():
     suite = unittest.TestSuite()
     suite.addTest(unittest.makeSuite(TestSetup))
     suite.addTest(unittest.makeSuite(TestSetupFailure))
+    suite.addTest(unittest.makeSuite(TestSingletonApp))
     suite.addTest(unittest.makeSuite(TestClientUtils))
     suite.addTest(unittest.makeSuite(TestLiveServer))
     suite.addTest(unittest.makeSuite(TestLiveServerOSPicksPort))
+    suite.addTest(unittest.makeSuite(TestLiveServerSingletonApp))
     suite.addTest(unittest.makeSuite(TestTeardownGraceful))
     suite.addTest(unittest.makeSuite(TestRenderTemplates))
     suite.addTest(unittest.makeSuite(TestNotRenderTemplates))

tests/test_utils.py

@@ -40,6 +40,22 @@ def test_remove_testcase_attributes(self):
 
         del self.app
 
+
+class TestSingletonApp(TestCase):
+    create_app_once = True
+    apps_created = 0
+
+    def create_app(self):
+        self.__class__.apps_created += 1
+        return create_app()
+
+    def test_create_app_once(self):
+        self.assertEqual(self.apps_created, 1)
+
+    def test_create_app_once_sanity(self):
+        # In case sorting method changes
+        self.assertEqual(self.apps_created, 1)
+
 class TestClientUtils(TestCase):
 
     def create_app(self):
@@ -245,6 +261,22 @@ def create_app(self):
         return app
 
 
+class TestLiveServerSingletonApp(BaseTestLiveServer):
+    create_app_once = True
+    apps_created = 0
+
+    def create_app(self):
+        self.__class__.apps_created += 1
+        return create_app()
+
+    def test_created_single_app(self):
+        self.assertEqual(1, self.apps_created)
+
+    def test_created_single_app_sanity(self):
+        # In case they run out of order
+        self.assertEqual(1, self.apps_created)
+
+
 class TestNotRenderTemplates(TestCase):
 
     render_templates = False