IssueTracker

Library used: com.android.support.test:rules
Version used: 0.3
Class in question: android.support.test.rule.ServiceTestRule

There appears to be a bug in ServiceTestRule.ProxyServiceConnection that introduces a race condition that causes ServiceTestRule.bindService() to sometimes (for me, often) return null after the first invocation.

The problem is that ServiceTestRule.ProxyServiceConnection defines the following static variable:

    public static CountDownLatch mConnectedLatch = new CountDownLatch(1);

This latch is decremented by one in onServiceConnected(), causing ServiceTestRule.bindService() to unblock and return the Binder.  However, since mConnectedLatch is declared as *static* its value is already zero the next time that ServiceTestRule.bindService() is invoked; this causes ServiceTestRule.bindService() to not wait at all for onServiceConnected() to be invoked and therefore often returns *before* it is invoked, in which case the Binder is null.

A possible fix might be to remove the "static" modifier from ServiceTestRule.ProxyServiceConnection.CountDownLatch

Here is a sample test that will expose the issue:

    @RunWith(AndroidJUnit4.class)
    public class TestBoundService {
   
        @Rule
        public final ServiceTestRule mServiceTestRule = new ServiceTestRule();
   
        @Test
        public void test1() throws Exception {
            assertBindServiceReturnsNonNull();
        }
   
        @Test
        public void test2() throws Exception {
            assertBindServiceReturnsNonNull();
        }
   
        private void assertBindServiceReturnsNonNull() throws Exception {
            final Context context = InstrumentationRegistry.getTargetContext();
            final Intent intent = new Intent(context, SomeService.class);
            final IBinder binder = mServiceTestRule.bindService(intent);
            assertNotNull(binder); // <-- this assertion will fail when the 2nd test is run
        }
   
    }

For now, as a workaround, I am binding to my service explicitly and not using ServiceTestRule, as I need to repeatedly bind to and unbind from my service in various tests in my test suite.