Espresso matchers

EditTextHasError.java

package com.djit.apps.karaokey.matcher;

import android.content.res.Resources;
import android.support.annotation.StringRes;
import android.support.test.espresso.matcher.BoundedMatcher;
import android.view.View;
import android.widget.EditText;

import org.hamcrest.Description;
import org.hamcrest.Matcher;

import static org.hamcrest.Matchers.is;

/**
 * A custom {@link org.hamcrest.Matcher} for Espresso that checks if an {@link android.widget.EditText}
 * displayds the right error message.
 */
public class EditTextHasError {

    private EditTextHasError() {
        //Non-instantiable
    }

    public static BoundedMatcher<View, EditText> withError(final CharSequence substring) {
        return withError(is(substring));
    }

    /**
     * Returns a matcher that matches {@link EditText}s based on text property value.
     *
     * @param stringMatcher : The {@link Matcher} of {@link String} with text to match.
     * @return : The newly created {@link Matcher}
     */
    private static BoundedMatcher<View, EditText> withError(final Matcher<CharSequence> stringMatcher) {
        return new BoundedMatcher<View, EditText>(EditText.class) {
            @Override
            protected boolean matchesSafely(EditText editText) {
                return stringMatcher.matches(editText.getError().toString());
            }

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

    /**
     * Returns a matcher that matches {@link EditText} based on the error string id.
     *
     * @param stringId : The ID of the string displayed as an error.
     * @return The newly created {@link Matcher}
     */
    public static BoundedMatcher<View, EditText> withError(@StringRes final int stringId) {
        return new BoundedMatcher<View, EditText>(EditText.class) {

            private String resourceName = null;
            private String expectedText = null;

            @Override
            protected boolean matchesSafely(EditText editText) {
                if (expectedText == null) {
                    try {
                        expectedText = editText.getResources().getString(stringId);
                        resourceName = editText.getResources().getResourceEntryName(stringId);
                    } catch (Resources.NotFoundException ignored) {
                        // view could be from a context unaware of the resource id
                    }
                }
                return null != expectedText && expectedText.equals(editText.getError());
            }

            @Override
            public void describeTo(Description description) {
                description.appendText("with error string id");
                description.appendValue(stringId);
                if (null != resourceName) {
                    description.appendText("[");
                    description.appendText(resourceName);
                    description.appendText("]");
                }
                if (null != expectedText) {
                    description.appendText(" value: ");
                    description.appendText(expectedText);
                }
            }
        };
    }

}