Testing failing because of java.lang.AssertionError: Activity never becomes requested state

I am new to instrumented tests and I am not able to have my very first test class to run. It is failing with this error:

java.lang.AssertionError: Activity never becomes requested state "[RESUMED, DESTROYED, STARTED, CREATED]" (last lifecycle transition = "PRE_ON_CREATE")

The test class is very simple, just contains a method to test a Fragment method that validates if the EditText are empty:

@RunWith(AndroidJUnit4.class)
public class CiudadFormularioFragmentInstrumentedTest {
    private FragmentScenario<CityFormFragment> fragmentScenario;

    @Before
    public void setUp() {
        // Launch the fragment
        fragmentScenario = FragmentScenario.launchInContainer(CityFormFragment.class);
    }

    @Test
    public void testValidate() {
        this.fragmentScenario.onFragment(CityFormFragment -> {
            assertTrue(CityFormFragment.validate());
        });
    }
}

The validate() method:

protected boolean validate() {
    boolean valid = true;
    for (int i = 0; i < this.mandatory.size(); i++) {
        View view = this.mandatory.get(i);
        if (view instanceof EditText) {
            if (TextUtils.isEmpty(((EditText) view).getText())) {
                ((EditText) view).setError(this.getResources()
                        .getString(R.string.missing_data));
                valid = false;
            }
        }
    }
    return valid;
}

Why test is failing with above error? I checked other posts with same error, but can't make mine to work.

By the way, I am running the test in an emulator.