Why espresso needs test method names to start with "test" even though it is using AndroidJunit4 runner?

I have been trying to run espresso tests using AndroidJunit4 runner. Here is my Test Class.

@RunWith(AndroidJUnit4.class)
public class MyActivityTest extends ActivityInstrumentationTestCase2<MyActivity> {
  public MyActivityTest() {
    super(MyActivity.class);
  }
  @Before
  public void setUp() throws Exception {
    super.setUp();
    injectInstrumentation(InstrumentationRegistry.getInstrumentation());
    getActivity();
  }
  @Test
  public void shouldAssert() {
    onView(withId(someId)).check(matches(isDisplayed()));
  }
}

I have been trying to run this test via ./gradlew connectedCheck from command line but for some reason it does not recognize this test.
I am able to run this test via Android Studio though.
If I rename my test method from shouldAssert to testShouldAssert gradle is able to recognize this as a test and runs it successfully.
I am puzzled since in Junit4 style test method names need not start with test.
Anybody has any idea about this?