JUnit Testcase Listeners Example

We all know how to write basic Junit testcases (if not then follow these links). I often found the use of listeners in application framework for several reasons including debugging the exact error point. It is one of common best practices in software industry.

Junit also provide support for adding listeners while executing the testcases via RunListener. This listener can be used for various purposes from improved logging to testcase specific logic.

I am writing two testclasses below for sample only. We will monitor the log printed for testcases in these classes.

package com.howtodoinjava.junit;

import junit.framework.Assert;

import org.junit.Test;

public class TestFeatureOne {
	@Test
	public void testFirstFeature()
	{
		Assert.assertTrue(true);
	}
}

package com.howtodoinjava.junit;

import junit.framework.Assert;

import org.junit.Ignore;
import org.junit.Test;

public class TestFeatureTwo {
	@Test
	public void testSecondFeature()
	{
		Assert.assertTrue(true);
	}

	@Test
	@Ignore
	public void testSecondFeatureIngored()
	{
		Assert.assertTrue(true);
	}
}

Lets write our listener. This listener will extend the RunListener class provided by Junit. You are free to override any number of methods including no method at all.

package com.howtodoinjava.junit.suite;

import org.junit.runner.Description;
import org.junit.runner.Result;
import org.junit.runner.notification.Failure;
import org.junit.runner.notification.RunListener;

public class ExecutionListener extends RunListener
{
	/**
	 * Called before any tests have been run.
	 * */
	public void testRunStarted(Description description)	throws java.lang.Exception
	{
		System.out.println("Number of testcases to execute : " + description.testCount());
	}

	/**
	 *  Called when all tests have finished
	 * */
	public void testRunFinished(Result result) throws java.lang.Exception
	{
		System.out.println("Number of testcases executed : " + result.getRunCount());
	}

	/**
	 *  Called when an atomic test is about to be started.
	 * */
	public void testStarted(Description description) throws java.lang.Exception
	{
		System.out.println("Starting execution of test case : "+ description.getMethodName());
	}

	/**
	 *  Called when an atomic test has finished, whether the test succeeds or fails.
	 * */
	public void testFinished(Description description) throws java.lang.Exception
	{
		System.out.println("Finished execution of test case : "+ description.getMethodName());
	}

	/**
	 *  Called when an atomic test fails.
	 * */
	public void testFailure(Failure failure) throws java.lang.Exception
	{
		System.out.println("Execution of test case failed : "+ failure.getMessage());
	}

	/**
	 *  Called when a test will not be run, generally because a test method is annotated with Ignore.
	 * */
	public void testIgnored(Description description) throws java.lang.Exception
	{
		System.out.println("Execution of test case ignored : "+ description.getMethodName());
	}
}

Now, lets run the testcases and observe the output.

package com.howtodoinjava.junit.suite;

import org.junit.runner.JUnitCore;

import com.howtodoinjava.junit.TestFeatureOne;
import com.howtodoinjava.junit.TestFeatureTwo;

public class ExecuteWithRunListener
{
	public static void main(String[] args)
	{
		JUnitCore runner = new JUnitCore();
		//Adding listener here
		runner.addListener(new ExecutionListener());
		runner.run(TestFeatureOne.class, TestFeatureTwo.class);
	}
}

Output:

Number of testcases to execute : 3
Starting execution of test case : testFirstFeature
Finished execution of test case : testFirstFeature
Starting execution of test case : testSecondFeature
Finished execution of test case : testSecondFeature
Execution of test case ignored : testSecondFeatureIngored
Number of testcases executed : 2

Clearly, adding listener provide extra control on testcase execution with improved logging support.

Happy Learning !!