Java App Engine integration testing with Spring MVC and OpenPersistenceManagerInViewFilter

In this post I’ll quickly show the technique I used for integration testing of Java services where the services rely on Spring data repositories being injected. We’re using Google’s App Engine to host and run our mobile sales dashboard for Magento/Amazon/Shopify so the tests will use the integration testing environment provided in the SDK.

Starting with a number of great articles on the subject I was able to quickly get a basic integration test up and running for App Engine with Spring. Our problem was related particularly to the PersistenceManager.

In the real application each web request is assigned a ThreadLocal PeristenceManager which is kept alive for the duration of that request, and always closed at the end, thanks to the OpenPersistenceManagerInViewFilter provided by Spring. So this is great when you’re calling data access methods on repositories from services in a web container, but means that if you’re trying to call those services during an integration test, the different repository calls will trigger exceptions that the objects involved belong to different PersistenceManagers.

The solution was to emulate the behavior of the OpenPersistenceManagerInViewFilter before and after a web request, in the setUp and tearDown of the tests themselves. For that I checked out the code for the filter and simply applied the same logic in the test.

First we make sure the Test class is setup to use Springs Junit functionality like below. Also note we are specifically setting the context to use the two test xml configurations. This is important because we actually wire a LocalPersistenceManagerFactoryBean in this Test class.

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(locations =  {"classpath:application-config-test.xml", "classpath:servlet-config-test.xml"})
public abstract class BaseSpringJunitTest
extends AbstractJUnit4SpringContextTests {
 
	@Autowired
	LocalPersistenceManagerFactoryBean pmf;
 
	// Standard App Engine integration testing helper
	protected final LocalServiceTestHelper helper =
			new LocalServiceTestHelper(new LocalDatastoreServiceTestConfig(), new
					LocalTaskQueueTestConfig(), new LocalMemcacheServiceTestConfig());
 
	// ...
}

Most of the test xml configuration is standard, the important bit is wiring in the bean, which should look familiar from your usual container deployment:

<bean class="org.springframework.orm.jdo.LocalPersistenceManagerFactoryBean" name="persistenceManagerFactory">
	<property name="persistenceManagerFactoryName" value="transactions-optional" />
</bean>

The setUp() just creates a new PersistenceManager (from the PMF we wired in) and stores it for use during the test (the same way the filter stores it for a web request).

@Before
public void setUp() {
    helper.setUp();
    PersistenceManager pm = PersistenceManagerFactoryUtils.getPersistenceManager(pmf.getObject(), true);
    TransactionSynchronizationManager.bindResource(pmf.getObject(), new PersistenceManagerHolder(pm));
}

In the tearDown() we’ll just do the same thing the filter does after the request.

@After
public void tearDown() {
	PersistenceManagerHolder pmHolder = 			(PersistenceManagerHolder)TransactionSynchronizationManager.unbindResource(pmf.getObject());
    PersistenceManagerFactoryUtils.releasePersistenceManager(pmHolder.getPersistenceManager(), pmf.getObject());
	helper.tearDown();
}

Once you have that class setup, you can extend it for your actual testing like this:

public class TestAccountService extends BaseSpringJunitTest {
 
	@Autowired
	private AccountService accountService;
 
	//..
 
	@Test
	public void testSubscribeNull() {
		accountService.subscribe(null, null);
		// check that subscribe behaved OK for null parameters...
	}
}

That’s it, go forth and test!. App Engine sure does make local integration testing and developing a local copy of your app easy and painless – I suggest you try it.

PS: This is the first Java development related post I have written in a long time, apologies to the Magento developer readers out there, it may not be the last.