Log messages in android studio junit test

Question

Is there a way to print out Logcat (Log.i, Log.d) messages when running a JUnit (method) test in Android Studio?

I can see System.out.print message but no logcat pri

Answer 1

I would go with @Vasiliy's approach but with a small change. Instead of using System.out.println for logging, we can actually use Java Logger configured with ConsoleHandler to log messages on the test output screen.

This can be achieved in below listed simple steps

Step 1: Define your own Log Level

  public enum LogLevel {
    VERBOSE,
    DEBUG,
    INFO,
    WARNING,
    ERROR,
    SILENT
}

Step 2: Define Logger abstraction

public abstract class Logger {

    ....

    public abstract void debug(String tag, String message);

    public abstract void error(String tag, String message);
   ....

}

Step 3: java.util.Logging based implementation for Logger

public class JavaLogger extends Logger {

    private java.util.logging.Logger mLogger;

    public JavaLogger(LogLevel logLevel, String name) {
        mLogger = java.util.logging.Logger.getLogger(name);
        ConsoleHandler handler = new ConsoleHandler();
        Level level = mapLogLevel(logLevel);
        handler.setLevel(level);
        mLogger.addHandler(handler);
        mLogger.setLevel(level);
    }

    @Override
    public void debug(String tag, String message) {
        if (isLoggable(LogLevel.DEBUG)) {
            mLogger.finer(message);
        }
    }

    @Override
    public void error(String tag, String message) {
        if (isLoggable(LogLevel.ERROR)) {
            mLogger.severe(message);
        }
    }

    ....

    private Level mapLogLevel(LogLevel logLevel) {
        Level level = Level.OFF;
        switch (logLevel) {
            case INFO:
                level = Level.INFO;
                break;

            case WARNING:
                level = Level.WARNING;
                break;

            case ERROR:
                level = Level.SEVERE;
                break;

            case VERBOSE:
                level = Level.FINEST;
                break;

            case DEBUG:
                level = Level.FINER;
                break;

            case SILENT:
                level = Level.OFF;
                break;

            default:
                // no impl
        }

        return level;
    }
}

Step 4: android.util.Log based implementation for Logger

public class AndroidLogger extends Logger {

public AndroidLogger(LogLevel logLevel) {
    super(logLevel);
}

 ....

@Override
public void debug(String tag, String message) {
    if (isLoggable(LogLevel.DEBUG)) {
        Log.d(tag, message, null);
    }
}

@Override
public void error(String tag, String message) {
    if (isLoggable(LogLevel.ERROR)) {
        Log.e(tag, message, tr);
    }
}

....

}

Step 5: Create a simple wrapper class for over Logger implementation

   public class AppLogger { 

    private static Logger sLogger;

   public static void init(Logger logger) {
        sLogger = logger;
    }

   public static void debug(final String tag, String message) {
        sLogger.debug(tag, message);
    }

    public static void error(final String tag, String message) {
        sLogger.error(tag, message, null);
    }

    public static void error(final String tag, String message, Throwable t) {
        sLogger.error(tag, message, t);
    }

    ... 
}

Step 6: Initialization

Android

Application onCreate method

AppLogger.init(new AndroidLogger(LogLevel.DEBUG));

Junit

AppLogger can be initialized in either @BeforeClass or @Before

AppLogger.init(new JavaLogger(LogLevel.DEBUG, "test-logger"));

Now you can observe the log message in Test Run Window of Android Studio