Wsrtjtyk

I am creating a simple layout that should support arabic language and RTL layout. Everything works fine. Now I want to write an Espresso test and assert weather it's actually showing the translated text or not. e.g. For arabic language it should display text from arabic strings.xml.

So far I tried below code as a TestRule.

public void setLocale(Locale locale) {

        Resources resources = InstrumentationRegistry.getTargetContext().getResources();

        Locale.setDefault(locale);

        Configuration config = resources.getConfiguration();

        config.locale = locale;

        resources.updateConfiguration(config, resources.getDisplayMetrics());

    }

The above code changes the layout direction but doesn't load resources from the localised directory.

I am not doing anything extra but something like http://www.andreamaglie.com/2016/a-test-rule-for-setting-device-locale/

Am I missing anything?

I've create a small test project using the link you provided for US and UK, the main classes are further down the answer, but it's a public project so you can just download it.

For 'AE' you will need to create a strings.xml under values-ar-rAE (see this link).
Edit: added another test for each language and MyActions class.

Credits: MyActions is from here, tests examples are from here, you might need to stop animation from the developer settings (from second link and here)

ForceLocaleRule:

import android.content.res.Configuration;

import android.content.res.Resources;

import android.support.test.InstrumentationRegistry;



import org.junit.rules.TestRule;

import org.junit.runner.Description;

import org.junit.runners.model.Statement;



import java.util.Locale;



public class ForceLocaleRule implements TestRule {



    private final Locale testLocale;

    private Locale deviceLocale;



    public ForceLocaleRule(Locale testLocale) {

        this.testLocale = testLocale;

    }



    @Override

    public Statement apply(final Statement base, Description description) {

        return new Statement() {

            public void evaluate() throws Throwable {

                try {

                    if (testLocale != null) {

                        deviceLocale = Locale.getDefault();

                        setLocale(testLocale);

                    }



                    base.evaluate();

                } finally {

                    if (deviceLocale != null) {

                        setLocale(deviceLocale);

                    }

                }

            }

        };

    }



    public void setLocale(Locale locale) {

        Resources resources = InstrumentationRegistry.getTargetContext().getResources();

        Locale.setDefault(locale);

        Configuration config = resources.getConfiguration();

        config.locale = locale;

        resources.updateConfiguration(config, resources.getDisplayMetrics());

    }



}

US test:

import android.content.Context;

import android.support.test.InstrumentationRegistry;

import android.support.test.rule.ActivityTestRule;

import android.support.test.runner.AndroidJUnit4;



import org.junit.Before;

import org.junit.ClassRule;

import org.junit.Rule;

import org.junit.Test;

import org.junit.runner.RunWith;



import java.util.Locale;



import static android.support.test.espresso.Espresso.onView;

import static android.support.test.espresso.action.ViewActions.closeSoftKeyboard;

import static android.support.test.espresso.assertion.ViewAssertions.matches;

import static android.support.test.espresso.matcher.ViewMatchers.withId;

import static android.support.test.espresso.matcher.ViewMatchers.withText;

import static example.com.testlocale.MyActions.setTextInTextView;

import static org.hamcrest.Matchers.containsString;

import static org.junit.Assert.assertEquals;



@RunWith(AndroidJUnit4.class)

public class MainActivityUsTest {



    @ClassRule

    public static final ForceLocaleRule localeTestRule = new ForceLocaleRule(Locale.US);



    @Rule

    public ActivityTestRule<MainActivity> myActivityRule = new ActivityTestRule<>(MainActivity.class);



    private Context context;



    @Before

    public void setUp() {

        context = InstrumentationRegistry.getTargetContext();

    }



    @Test

    public void testAirplaneEn() {

        assertEquals("airplane", context.getString(R.string.airplane));

    }



    @Test

    public void testAirplaneEnOnView() {

        onView(withId(R.id.text_view))

                .perform(setTextInTextView(context.getString(R.string.airplane)),

                        closeSoftKeyboard());

        onView(withId(R.id.text_view))

                .check(matches(withText(containsString("airplane"))));

    }



}

UK test:

import android.content.Context;

import android.support.test.InstrumentationRegistry;

import android.support.test.rule.ActivityTestRule;

import android.support.test.runner.AndroidJUnit4;



import org.junit.Before;

import org.junit.ClassRule;

import org.junit.Rule;

import org.junit.Test;

import org.junit.runner.RunWith;



import java.util.Locale;



import static android.support.test.espresso.Espresso.onView;

import static android.support.test.espresso.action.ViewActions.closeSoftKeyboard;

import static android.support.test.espresso.assertion.ViewAssertions.matches;

import static android.support.test.espresso.matcher.ViewMatchers.withId;

import static android.support.test.espresso.matcher.ViewMatchers.withText;

import static example.com.testlocale.MyActions.setTextInTextView;

import static org.hamcrest.Matchers.containsString;

import static org.junit.Assert.assertEquals;



@RunWith(AndroidJUnit4.class)

public class MainActivityGbTest {



    @ClassRule

    public static final ForceLocaleRule localeTestRule = new ForceLocaleRule(Locale.UK);



    @Rule

    public ActivityTestRule<MainActivity> myActivityRule = new ActivityTestRule<>(MainActivity.class);



    private Context context;



    @Before

    public void setUp() {

        context = InstrumentationRegistry.getTargetContext();

    }



    @Test

    public void testAirplaneEnGB() {

        assertEquals("aeroplane", context.getString(R.string.airplane));

    }



    @Test

    public void testAirplaneEnOnView() {

        onView(withId(R.id.text_view))

                .perform(setTextInTextView(context.getString(R.string.airplane)),

                        closeSoftKeyboard());

        onView(withId(R.id.text_view))

                .check(matches(withText(containsString("aeroplane"))));

    }



}

MyActions:

import android.support.test.espresso.UiController;

import android.support.test.espresso.ViewAction;

import android.view.View;

import android.widget.TextView;



import org.hamcrest.Matcher;



import static android.support.test.espresso.matcher.ViewMatchers.isAssignableFrom;

import static android.support.test.espresso.matcher.ViewMatchers.isDisplayed;

import static org.hamcrest.CoreMatchers.allOf;



public class MyActions {



    public static ViewAction setTextInTextView(final String value){

        return new ViewAction() {

            @SuppressWarnings("unchecked")

            @Override

            public Matcher<View> getConstraints() {

                return allOf(isDisplayed(), isAssignableFrom(TextView.class));

            }



            @Override

            public void perform(UiController uiController, View view) {

                ((TextView) view).setText(value);

            }



            @Override

            public String getDescription() {

                return "set text to TextView";

            }

        };

    }



}

values-en-rUSstrings.xml

<resources>

    <string name="app_name">TestLocale</string>

    <string name="airplane">airplane</string>

</resources>

values-en-rGBstrings.xml

<resources>

    <string name="app_name">TestLocale</string>

    <string name="airplane">aeroplane</string>

</resources>