Appium Desired Capabilities

Detailed explanation

Appium Desired Capabilities are fundamental to setting up and configuring Appium test sessions. They act as a negotiation mechanism between your test script and the Appium server, informing the server about the specific environment and application you intend to test. Without properly configured desired capabilities, Appium won't know how to launch your app, which device or emulator to use, or other crucial settings, leading to test failures.

Think of desired capabilities as a configuration file passed to the Appium server at the start of a test session. This configuration file tells Appium everything it needs to know to correctly initialize the test environment.

Key Capabilities and Their Usage

Several core desired capabilities are commonly used across different platforms (Android and iOS). Here's a breakdown of some of the most important ones:

• platformName: Specifies the operating system you want to automate. Common values are Android or iOS.

  capabilities.setCapability("platformName", "Android");

• platformVersion: Specifies the version of the operating system you want to use. This is useful for targeting specific OS versions.

  capabilities.setCapability("platformVersion", "13");

• deviceName: Specifies the name of the device or emulator you want to use. For emulators, this can be a generic name like Pixel_3a_API_33. For real devices, you'll need to use the device's actual name (obtainable through ADB for Android or Xcode for iOS).

  capabilities.setCapability("deviceName", "Pixel_3a_API_33");

• appPackage (Android only): Specifies the package name of the Android application you want to test. You can find this in the AndroidManifest.xml file or by using ADB commands.

  capabilities.setCapability("appPackage", "com.example.myapp");

• appActivity (Android only): Specifies the activity you want to launch when the app starts. This is usually the main activity of your application.

  capabilities.setCapability("appActivity", "com.example.myapp.MainActivity");

• bundleId (iOS only): Specifies the bundle identifier of the iOS application you want to test. This is similar to appPackage on Android.

  capabilities.setCapability("bundleId", "com.example.myapp");

• app: Specifies the absolute path to the application file (.apk for Android, .ipa for iOS). This is an alternative to using appPackage and appActivity (or bundleId) if you want Appium to install the app directly.

  capabilities.setCapability("app", "/path/to/your/app.apk");

• udid: Specifies the unique device identifier (UDID) of the device you want to use. This is necessary when you have multiple devices connected to your machine.

  capabilities.setCapability("udid", "your_device_udid");

• automationName: Specifies the automation engine you want to use. For Android, common values are UiAutomator2 (recommended for newer Android versions) or UiAutomator. For iOS, the value is XCUITest.

  capabilities.setCapability("automationName", "UiAutomator2");

• noReset: Prevents Appium from resetting the application state before and after each test session. Setting this to true can speed up test execution.

  capabilities.setCapability("noReset", true);

• fullReset: Forces Appium to completely uninstall and reinstall the application before each test session. This ensures a clean state but can be slower.

  capabilities.setCapability("fullReset", true);

Practical Implementation with Java and Selenium

Here's an example of how to set up desired capabilities using Java and Selenium:

import io.appium.java_client.android.AndroidDriver;
import org.openqa.selenium.remote.DesiredCapabilities;
import java.net.MalformedURLException;
import java.net.URL;
 
public class AppiumSetup {
 
    public static void main(String[] args) throws MalformedURLException {
 
        DesiredCapabilities capabilities = new DesiredCapabilities();
        capabilities.setCapability("platformName", "Android");
        capabilities.setCapability("platformVersion", "13");
        capabilities.setCapability("deviceName", "Pixel_3a_API_33");
        capabilities.setCapability("appPackage", "com.android.calculator2");
        capabilities.setCapability("appActivity", "com.android.calculator2.Calculator");
        capabilities.setCapability("automationName", "UiAutomator2");
 
        AndroidDriver driver = new AndroidDriver(new URL("http://127.0.0.1:4723/wd/hub"), capabilities);
 
        // Now you can use the 'driver' object to interact with the app
 
        driver.quit();
    }
}

Best Practices

• Start with the essentials: Begin by setting the minimum required capabilities like platformName, deviceName, appPackage (or bundleId), and appActivity (or bundleId).
• Use specific versions: Specify platformVersion to target specific OS versions and avoid unexpected behavior due to OS differences.
• Leverage noReset and fullReset wisely: Use noReset to speed up tests when a clean state isn't necessary. Use fullReset only when you need to ensure a completely fresh application installation.
• Handle device variations: Use conditional logic in your test setup to handle different device types and screen sizes. You might need different locators or strategies for different devices.
• Store capabilities in a configuration file: Avoid hardcoding capabilities directly in your test scripts. Instead, store them in a configuration file (e.g., a properties file or a JSON file) to make them easier to manage and modify.
• Use environment variables: Utilize environment variables to configure capabilities that might change depending on the environment (e.g., the Appium server address).
• Read Appium logs: If you encounter issues, carefully examine the Appium server logs. They often contain valuable information about why a test session failed to start or why a particular capability was not recognized.

Common Tools

• Appium Inspector: A GUI tool that allows you to inspect the UI hierarchy of your application and generate desired capabilities. This is extremely helpful for identifying element locators and determining the correct appPackage and appActivity (or bundleId).
• ADB (Android Debug Bridge): A command-line tool that allows you to interact with Android devices and emulators. You can use ADB to find the appPackage and appActivity of an application.
• Xcode (for iOS): The integrated development environment (IDE) for iOS development. You can use Xcode to find the bundleId of an iOS application.

By understanding and effectively utilizing Appium Desired Capabilities, you can create robust and reliable mobile automation tests that accurately reflect the behavior of your application across different devices and platforms.

Further reading

• Appium Documentation: http://appium.io/docs/en/
• Appium Desired Capabilities: http://appium.io/docs/en/writing-running-appium/caps/