Using espresso view matcher with hamcrest matchers

Issue

Can someone please tell me why does not this works

onView(withId(R.id.edt_apikey)).check(matches(hasErrorText(anyString())));

Shows this in logcat:

android.support.test.espresso.base.DefaultFailureHandler$AssertionFailedWithCauseError: 'with error: is ""' doesn't match the selected view.
Expected: with error: is ""
Got: "AppCompatEditText{id=2131492985, res-name=edt_apikey, visibility=VISIBLE, width=517, height=83, has-focus=false, has-focusable=true, has-window-focus=true, is-clickable=true, is-enabled=true, is-focused=false, is-focusable=true, is-layout-requested=false, is-selected=false, root-is-layout-requested=false, has-input-connection=true, editor-info=[inputType=0x80001 imeOptions=0xc000005 privateImeOptions=null actionLabel=null actionId=0 initialSelStart=0 initialSelEnd=0 initialCapsMode=0x0 hintText=1c915e3b5d42d05136185030892fbb846c278927 label=null packageName=null fieldId=0 fieldName=null extras=null ], x=139.0, y=83.0, text=, error-text=This field is required, hint=1c915e3b5d42d05136185030892fbb846c278927, input-type=524289, ime-target=false, has-links=false}"

I guess the above doesn't work since it was a Mockito matcher. So I tried this:

    import static android.support.test.espresso.matcher.ViewMatchers.hasErrorText;
import static org.hamcrest.Matchers.isEmptyOrNullString;
import static org.hamcrest.Matchers.notNullValue;
import static org.hamcrest.Matchers.nullValue;

onView(withId(R.id.edt_apikey)).check(matches(hasErrorText(not(isEmptyOrNullString()))));

And it doesn't works either. Giving this exception...

java.lang.NullPointerException: Attempt to invoke interface method 'java.lang.String java.lang.CharSequence.toString()' on a null object reference
                                                                     at android.support.test.espresso.matcher.ViewMatchers$34.matchesSafely(ViewMatchers.java:1130)
                                                                     at android.support.test.espresso.matcher.ViewMatchers$34.matchesSafely(ViewMatchers.java:1120)

Solution

The temporary solution is to create a custom matcher

public static Matcher<View> hasErrorText(final Matcher<String> stringMatcher) {
    checkNotNull(stringMatcher);
    return new BoundedMatcher<View, EditText>(EditText.class) {

        @Override
        public void describeTo(Description description) {
            description.appendText("with error: ");
            stringMatcher.describeTo(description);
        }

        @Override
        protected boolean matchesSafely(EditText view) {
            if (view.getError() == null) return stringMatcher.matches(view.getError());
            return stringMatcher.matches(view.getError().toString());
        }
    };
}

And then use it like onView(withId(R.id.edt_apikey)).check(matches(hasErrorText(not(Matchers.isEmptyOrNullString()))));

Answered By - JehandadK