Language and locale automated testing on mobile apps

The terms locale and language are often used in the same context, but they have different meanings.

The term language indicates the language on the device. It is the language used in the UI of the device's OS and can often be changed in the Settings menu of your OS.
Examples of a language are: English, French, Portugese, Dutch, Spanish, Chinese and more. iOS supports more than 30 languages, while Android supports a larger amount of languages.

Locale refers to regional settings, for a specific country or place. This includes settings such as currency format, number format, or date formats.
Countries can share the same language, but have different locale settings.

To get a list of available locales on Android, you can use this snippet of code:

for (Locale locale : Locale.getAvailableLocales()) {
	Log.d("LOCALES", locale.getLanguage() + "_" + locale.getCountry() + " [" + locale.getDisplayName() + "]");
}

Appium provides a language capability, which you can use to pass in the desired language code (ISO 639-1) of the app under test.

When you compile your IPA or APK file, you can indicate which languages you want to support and provide the translated content.
For Android, translated content usually appears in strings.xml files, while on iOS you can use XCode's localization features.

DesiredCapabilities desiredCapabilities = new DesiredCapabilities();
desiredCapabilities.setCapability("language", "es");

To fetch a all translated strings for a specific language, you can use the app_strings command:

let appStrings = driver.getStrings("<language_code>");

To change the locale, you can use Appium's locale capability, which accepts region codes.

By changing the locale, you can test regional settings, such as currency formats, date formats, time and calendar formats.
All these settings are country/region specific and can be tested with Appium's locale capability.

DesiredCapabilities desiredCapabilities = new DesiredCapabilities();
desiredCapabilities.setCapability("locale", "fr_CA");

Changing the language or locale will change the settings on a device level for Android, and on an app-level for iOS.

XCUITest offers two arguments which you can use to set the language or locale:

• -AppleLanguages
• -AppleLocale

To use this in XCUITest, you can pass in a language or locale of your choosing like this:

XCUIApplication().launchArguments += [“-AppleLanguages”, “(fr)”]
XCUIApplication().launchArguments += [“-AppleLocale”, “fr_FR”]
XCUIApplication().launch()

In the example above, we set the language to French and the locale to France/French.
XCUITest will open the app with these settings. If your app has localized strings for this language, your app should display in the correct language.

Apple provides some more information about setting up and testing localized apps in their Testing your International App documentation.

During an Espresso test, you can programmaticaly switch the language or locale of the app.
Please see the example below on how to achieve this:

private void setLocale(String language, String country) {
    Locale locale = new Locale(language, country);
    // here we update locale for date formatters

    Locale.setDefault(locale);
    // here we update locale for app resources

    Resources res = getContext().getResources();
    Configuration config = res.getConfiguration();
    config.locale = locale;
    res.updateConfiguration(config, res.getDisplayMetrics());
}

This function accepts a language and country, it will update the locale and resources during the Espresso test.