AndroidX Test

Detailed explanation

AndroidX Test is a comprehensive testing framework designed to facilitate various types of testing for Android applications. It's part of the Android Jetpack suite and offers a consistent and modern approach to testing compared to older testing support libraries. It provides a unified set of APIs for UI testing, unit testing, and integration testing, making it easier for developers to write and maintain tests.

Key Components of AndroidX Test

AndroidX Test comprises several key components, each serving a specific purpose in the testing process:

• Espresso: Espresso is a UI testing framework that allows you to write concise and reliable UI tests. It provides APIs to interact with UI elements, assert their state, and synchronize with UI events. Espresso is known for its automatic synchronization, which ensures that tests only interact with the UI when it's idle, reducing flakiness.

• UI Automator: UI Automator is another UI testing framework that enables you to test across app boundaries and system apps. It provides APIs to interact with any visible UI element, regardless of which app owns it. UI Automator is particularly useful for testing complex workflows that involve multiple apps or system dialogs.

• AndroidJUnitRunner: AndroidJUnitRunner is a JUnit test runner for Android. It provides the infrastructure to run JUnit tests on Android devices or emulators. It also supports features like code coverage and test filtering.

• Truth: Truth is a fluent assertion library that makes it easier to write readable and maintainable assertions in your tests. It provides a rich set of assertion methods for various data types and objects.

Setting up AndroidX Test

To use AndroidX Test in your project, you need to add the necessary dependencies to your build.gradle file. Here's an example of how to add the dependencies for Espresso, UI Automator, and JUnit:

dependencies {
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.5.1'
    androidTestImplementation 'androidx.test.ext:junit:1.1.5'
    androidTestImplementation 'androidx.test.uiautomator:uiautomator:2.2.0'
    testImplementation 'junit:junit:4.13.2'
}

Make sure to sync your Gradle project after adding the dependencies.

Writing UI Tests with Espresso

Espresso is a powerful tool for writing UI tests that simulate user interactions with your app. Here's a simple example of an Espresso test that clicks a button and verifies that the text in a TextView changes:

import androidx.test.espresso.Espresso;
import androidx.test.espresso.action.ViewActions;
import androidx.test.espresso.assertion.ViewAssertions;
import androidx.test.espresso.matcher.ViewMatchers;
import androidx.test.ext.junit.rules.ActivityScenarioRule;
import androidx.test.ext.junit.runners.AndroidJUnit4;
 
import org.junit.Rule;
import org.junit.Test;
import org.junit.runner.RunWith;
 
@RunWith(AndroidJUnit4.class)
public class ExampleInstrumentedTest {
 
    @Rule
    public ActivityScenarioRule<MainActivity> activityRule =
            new ActivityScenarioRule<>(MainActivity.class);
 
    @Test
    public void testButtonClick() {
        // Find the button and click it
        Espresso.onView(ViewMatchers.withId(R.id.button)).perform(ViewActions.click());
 
        // Verify that the text in the TextView has changed
        Espresso.onView(ViewMatchers.withId(R.id.textView))
                .check(ViewAssertions.matches(ViewMatchers.withText("Button Clicked!"));
    }
}

In this example, Espresso.onView() is used to find UI elements by their ID. ViewActions.click() performs a click action on the button. ViewAssertions.matches() verifies that the text in the TextView matches the expected value.

Writing UI Tests with UI Automator

UI Automator is useful for testing scenarios that involve multiple apps or system dialogs. Here's an example of a UI Automator test that opens the settings app and navigates to the "About phone" section:

import androidx.test.uiautomator.UiDevice;
import androidx.test.uiautomator.UiObject;
import androidx.test.uiautomator.UiSelector;
 
import org.junit.Test;
import org.junit.runner.RunWith;
import androidx.test.ext.junit.runners.AndroidJUnit4;
import androidx.test.platform.app.InstrumentationRegistry;
 
@RunWith(AndroidJUnit4.class)
public class UiAutomatorTest {
 
    @Test
    public void testOpenSettings() throws Exception {
        UiDevice device = UiDevice.getInstance(InstrumentationRegistry.getInstrumentation());
 
        // Open the Settings app
        device.pressHome();
        UiObject allAppsButton = device.findObject(new UiSelector().description("Apps list"));
        allAppsButton.click();
 
        UiObject settingsApp = device.findObject(new UiSelector().text("Settings"));
        settingsApp.click();
 
        // Navigate to About phone
        UiObject aboutPhone = device.findObject(new UiSelector().text("About phone"));
        aboutPhone.click();
 
        // Verify that we are in the About phone section (example: check for a specific text)
        UiObject statusInformation = device.findObject(new UiSelector().text("Status information"));
        statusInformation.exists();
    }
}

In this example, UiDevice.getInstance() is used to get an instance of the UI device. device.findObject() is used to find UI elements by their text or description. object.click() performs a click action on the UI element.

Best Practices for AndroidX Test

• Write small, focused tests: Each test should focus on a specific aspect of your app's functionality. This makes it easier to identify and fix issues.
• Use descriptive test names: Test names should clearly describe what the test is verifying.
• Avoid hardcoding values: Use constants or resource values instead of hardcoding values in your tests.
• Use mocks and stubs: Use mocks and stubs to isolate the code under test and avoid dependencies on external resources.
• Run tests frequently: Run your tests frequently to catch issues early in the development process.
• Keep your tests up to date: Update your tests whenever you make changes to your app's code.
• Use Page Object Model: For UI tests, consider using the Page Object Model to create reusable and maintainable test code.

Common Tools and Libraries

• Mockito: A popular mocking framework for Java and Android.
• Robolectric: A framework that allows you to run Android tests on the JVM without an emulator or device.
• AssertJ: Another fluent assertion library that provides a rich set of assertion methods.
• Barista: An Espresso extension library that provides a more concise and readable syntax for writing UI tests.

By following these best practices and utilizing the available tools and libraries, you can write robust and reliable tests for your Android applications using AndroidX Test. This will help you ensure the quality of your app and deliver a better user experience.

Further reading

• Android Developers - Testing Overview
• AndroidX Test Library
• Espresso Documentation
• UI Automator Documentation