JUnit: Excluding data driven tests

Once in a while there is that single test case that cannot be executed for certain data when running data driven tests. This could be a true  annoyment and it is tempting to break out those tests into a separate test class, don’t do that and stay away from taking shortcuts that will give you;

  • False test statistics, reporting passing test that has never been run
  • Avoid Ignoring tests e.g. using conditional ignores or JUnit’s assume.

A simple way to exclude a test from being executed when running data driven tests using the Parameterized.class is to set up a conditional JUnit rule. A test rule that based on the current test data in the data driven loop runs OR excludes a specifc test.

Consider the scenario below

We run the all tests below with the following samples “a”, “b”, “c” but know that test02 will not work for the sample “b” so we will have to deal with that in a clever way.

public class Test {

  private String sample;

  public Test(String sample) {
    this.sample = sample;

  public static Collection<Object[]> generateSamples() {
    final List <Object[]> samples = new ArrayList<Object[]>();
    sample.add(new Object[]{"a"});
    sample.add(new Object[]{"b"});
    sample.add(new Object[]{"c"});
    return samples;

  public void test01() {
    // Works with sample "a", "b", "c"

  public void test02() {
    // Works with sample "a", "c" BUT NOT "b"

  public void test03() {
    // Works with sample "a", "b", "c"

Mark-up with test annotation

Step one is to mark-up a test case so that we know that it will only run for certain samples. We will do this by adding an annotation, in this case we call it Samples.

public void test01() { ... }

public void test02() { ... }

public void test03() { ... }

Using the test annotation Samples we can start filtering during run-time if to execute a test case or not. A test without the annotation will always run the test no matter what data that is reurned in the data driven loop. If the annotation is in place the test will only run for the samples that matches the values in the annotation. In case of test02 it will only run for samples “a” and “c”.

The test annotation

Adding the annotation is straight forward, read up on it here.

public @interface Samples {
    String [] value();

Adding the exclusion rule

Worth knowing is that JUnit rules will always be created before a test class constructor. This means that a rule will not know the test data sample of the current data driven iteration. The current data driven value is always passed to the test class constructor (Parameterized.class) and hence the rule we are going to implement needs to get that information as well at that point.

public class Test {

  public OnlyRunForSampleRule rule = new OnlyRunForSampleRule();
  private String sample;

  public Test(String sample) {
    this.sample = sample;
    rule.setSample(sample); // <<-- HERE

With the current data sample and the Samples annotation values known at run-time, we define a simple rule that excludes test cases if they are not supposed to run for certain test data.

public class OnlyRunForSampleRule implements TestRule {

  private String sample;

  public Statement apply(Statement s, Description d) {
    Protocols annotation = d.getAnnotation(Samples.class);
    // No annotation/samples matching, always run
    if (annotation == null) {
      return s;
    // Match! One sample value matches current parameterized sample value
    else if (Arrays.asList(annotation.value()).contains(protocol)) {
      return s;
    // No match in the samples annotation, skipping
    return new Statement() {
      public void evaluate() throws Throwable {}

  public void setSample(String sample) {
    this.sample = sample;

The rule above is defined to run tests on known samples, creating the inverse of this rule is simply done by returning the empty Statement in the else if that checks for matches in the Samples annotation.

Debugging WireMock calls when using JUnit WireMockRule

Mocking using the WireMockRule in your JUnit test classes and struggle with 404’s?

It is not that trivial to find in the WireMock documentation but it is in there, under ‘Listening for requests’ @ http://wiremock.org/verifying.html. Plain debugging fine, but sometimes one really wants to know the details of the calls made to the underlying services that are consumed, especially when WireMocking these services and there is a fine grained matching mechanism to deal with.

Below is the quick awesome tip to get the details you need to resolve the WireMock returned 404’s easily.

Add a request listener to your WireMockRule and Use Java 8 lambdas to smoothly implement the WireMock interface RequestListener that has the single method requestReceived(Request request, Response response). Print out the reponse and request details you want. Run your tests and check the print outs, all set!

import com.github.tomakehurst.wiremock.junit.WireMockRule;

public class Test {

   public WireMockRule wireMockRule = new WireMockRule(6969);

   public void setupTest() {
      wireMockRule.addMockServiceRequestListener((request, response) -> {
         System.out.println("URL Requested => " + request.getAbsoluteUrl());
         System.out.println("Request Body => " + request.getBodyAsString());
         System.out.println("Request Headers => " + request.getAllHeaderKeys());
         System.out.println("Response Status => " + response.getStatus());
         System.out.println("Response Body => " + response.getBodyAsString());

Bundling ChromeDriver with your test code

This post will just exemplify one way of maintaining the chrome drivers used for running automated tests with WebDriver and the Chrome browser without having to update and install the ChromeDriver to all possible nodes where tests will be running. The ChromeDriver will simply be bundled with the running tests and put under source control as for all other test ware.

Downloading links

Start by putting the the drivers under the resource folder so that they will be picked up by Maven per default.

<project root>/src/main/resources/chromedriver/mac/chromedriver
<project root>/src/main/resources/chromedriver/windows/chromedriver.exe

There are of course different drivers for different OS types and this needs to be handled using the os.name system property.

As per the ChromeDriver usage instructions (here) a system property has to be set pointing to the ChromeDriver server to use for the Chrome browser bridging. We will not point to a fixed location in the file system, instead well get the path by using the Class.getResource which will enable us to bundle ChromeDriver inside our test framework even if it is bundled into a jar file.

Basically what should be done are the following steps.

  • Determine OS type
  • Get the Chrome Driver resource and make sure it is executable using File.setExecutable(true). This is due to when packaged in a jar the execution attributes ‘x’ will be removed on Mac (and assumed on Linux too).
  • Set the “web driver.chrome.driver” system property.
  • Check that a Chrome installation exists in the default location [OPTIONAL]
private static WebDriver driver = null;
// The ChromeDriver locations under the resource folder
private static String MAC_DRIVER = "/chromedriver/mac/chromedriver";
private static String WINDOWS_DRIVER = "/chromedriver/windows/chromedriver.exe";

public static void setupChromeDriver() {
   // OS type
   if (System.getProperty("os.name").contains("Mac")) {
      File cDriver = new File(Tester.class.getResource(MAC_DRIVER).getFile());

      // Is it executable
      if (!cDriver.canExecute()) {
      System.setProperty("webdriver.chrome.driver", Tester.class.getResource(MAC_DRIVER).getFile());

      // Now checking for existence of Chrome executable.'
      if (!new File("/Applications/Google Chrome.app/Contents/MacOS/Google Chrome").exists()) {
         throw new RuntimeException(errorMessage);
   } else {
      System.setProperty("webdriver.chrome.driver", Tester.class.getResource(WINDOWS_DRIVER).getFile());

      // Now checking for existence of Chrome executable.'
      if (!new File(System.getProperty("user.home") + "/AppData/Local/Google/Chrome/Application/chrome.exe").exists()) {
         throw new RuntimeException(errorMessage);

   ChromeOptions options = new ChromeOptions();
   driver = new ChromeDriver(options);

Test case example
Pretty straight on from here, setup WebDriver through the implemented method above and run a simple open page test to see that things worked out.

private static WebDriver driver = null;
public static void setupChromeDriver(){

public static void setupTestClass() throws Exception {

public void demoTestCase() throws Exception {

JUnit @Rule for printing test case start and end information

If you are watching the test execution trace during run-time and is missing the information about when a test cases starts and ends, then it can be easily fixed by adding a JUnit rule that prints out this information.

[TEST START] tc_shallPass
stuff printed during execution
[TEST ENDED] Time elapsed: 1.835 sec

The start and end tags gets generated automatically and hence no need to add any test case specific printing.

public void tc_shallPass() {
	System.out.println("stuff printed during execution");

To hook up the rule to all test cases in a class it has to be declared and instantiated first.

public class TestClass {
	public TestCasePrinterRule pr = new TestCasePrinterRule(System.out);
	// @Test
	// ...

So far so good, but how is this claimed to be “easily fixed” rule implemented then? Pretty straight forward by implmenting the org.junit.rules.TestRule and using a private class extending the org.junit.rules.ExternalResource. The example below calculates the execution time for the test case as well as providing the name of the current test case.

During run-time the start message will be printed before any other @Before annotated methods in the class but after the @BeforeClass methods. The apply method handles the creation of start and end tags since it has access to the test case description content, org.junit.runner.Description. The actual printing is done in the overridden before and after methods.

package com.yourcompany.customrules;

import java.io.IOException;
import java.io.OutputStream;
import java.text.DecimalFormat;

import org.junit.rules.ExternalResource;
import org.junit.rules.TestRule;
import org.junit.runner.Description;
import org.junit.runners.model.Statement;

public class TestCasePrinterRule implements TestRule {

    private OutputStream out = null;
    private final TestCasePrinter printer = new TestCasePrinter();

    private String beforeContent = null;
    private String afterContent = null;
    private long timeStart;
    private long timeEnd;
    public TestCasePrinterRule(OutputStream os) {
        out = os;

    private class TestCasePrinter extends ExternalResource {
        protected void before() throws Throwable {
            timeStart = System.currentTimeMillis();

        protected void after() {
            try {
                timeEnd = System.currentTimeMillis();
                double seconds = (timeEnd-timeStart)/1000.0;
                out.write((afterContent+"Time elapsed: "+new DecimalFormat("0.000").format(seconds)+" sec\n").getBytes());
            } catch (IOException ioe) { /* ignore */

    public final Statement apply(Statement statement, Description description) {
        beforeContent = "\n[TEST START] "+description.getMethodName()+"\n"; // description.getClassName() to get class name
        afterContent =  "[TEST ENDED] ";
        return printer.apply(statement, description);

Using JUnit @Category and Maven profiles to get stable test suites

Since it happens over and over again, no matter what project I am in. Keeping the test suites green and passing is a …

The blind eye

The one sneaking little test case that starts failing can prove to be a real killer to all automation approaches. More than once it has shown that as soon as a single test case breaks a test suite things starts to go downhill, fast. Ok, there could be acceptable resons for the test case to be broken, e.g. if there are issues in the system under test or in the test framework that are not bugs.

The usual decision taken is to leave the test case as is for now since we are all aware that it will fail for a while, BAD choice!!! All attention on the failing test suite is moving from slight attention to abandoned, and if other test in the test same test suite starts failing for various reasons it will most likely go by undetected.

What can/should be done here

  • Disable the test case and enable it again when it should be back on track
  • Maintain test suites to allow it to execute and fail but in a another suite/run to keep the MUST always pass test suites all green

The later case is the way to go.

Maven profiles to your rescue

Using Maven profiles it is easy to group your JUnit test classes and test cases in different categories. Usually this is used for grouping tests into slow, fast and browser-less tests a.s.f.. This approach can be stretched even further by using a grouping that reflects the current state of the test case. There does not have to be that many different groupable categories but at least two is needed.

  • Stable
  • Unstable/Maturing

Stable is self explained while Unstable/Maturing covers everything that is NOT always PASSING. It might be test cases that are unstable beacuse of;

  • timing issues
  • tested functionality is still under development (during sprints)
  • there is a low priority bug that will be fixed later
  • unknown issues causing it to sporadically fail
  • waiting to get a STABLE stamp

Use case 1
The last item is an approach that can be used to be really be sure that the stable test suites does not get polluted. Any new test case needs to run a set number of times (e.g. 20) in a test suite and must pass all all times before being stamped as a reliable test case.

Use case 2
When a bug surfaces that causes a test case to fail it might sometimes be the case that it wont be fixed for some time period. Instead of totally disabling or trying to fix the test case that would fail an otherwise stable test suite it shall be moved to an unstable test suite. This is a way to put the test case in a quarantine until the bug has been fixed and on the same tame make sure it still compiles and is executable.

Categorizing tests using JUnit @Category annotation
Use the JUnit @Category annotation in front of your test cases or test classes.

public void aTestCase() {
  // void

// Alternatively an unstable test case

public void anotherTestCase() {
  // void

Splitting test execution using Maven profiles

Configure your Surefire plugin to include and exclude certain test classes as well as determine a set of JUnit @Category groups to be included in the test run. Set up your pom including profiles as examplified below.


The testcase.groups property can be used to define a set of groups (JUnit @Categories) to include when tests using the actual profile.


Packaging and referencing images for Sikuli based tests in artifacts

This post describes one approach for packaging/bundling image resources used for Sikuli based automated test cases.

  • Bundling images as resources
  • Retrieveing/using image resources

That the images used when automating tests using Sikuli needs to versioned should be rather obvious. Naturally the majority of the pictures used in test cases reflects part of the system under test and hance shall be treated and handled as a part of the test code synchronized with what we are actually testing against. This is usually solved by having the test code in the same repository as the code under test, though it might not always be the case.

In a current test setup it was not possible to keep the test code and images together with the code under test so the test code had to be distrubited as an versioned artifact/jar-file.

Test artifact

One if the easier ways for avoiding a lot of test case maintenance is to wrap the interface to the system under test in to an artifact/API/jar-file. This allows for the artifact to be shared between different source control repositories and included in automated tests residing elsewhere (usual scenario when there are multiple trunks and components in a system). For the artifact approach the images to use for the Sikuli based tests needs to be a part of this artifact.

Bundling the images
Out of the box really, well if you are using Maven. Just put the images under resources and they gets bundled correctly in the jar. The location in the repository should be something like this.

  \- java
      \- org.project.example
  \- resources\images
      \- theImageToLookFor.PNG
      \- otherImage.PNG
      \- ...

That is all there is to it, now distribute the artifact freely, a complete pom for building a complete Sikuli test artifact including images is posted at the end.

Accessing the images in the test code
To be able to reference and use the images in your test there needs to be functionality in the artifact for getting the image resource. So implement a generic getter method that picks up all images correctly for you from inside the jar/artifact during run-time.

class TestArtifact {
	// Image file name must start with the '/' and the image name is
	// case sensitive so be thorough when using.
	private Pattern getPattern(String fileName) throws IOException {
	   BufferedImage image = ImageIO.read(getClass().getResource(fileName));
	   return new Pattern(image);

	// Example method using an image.
	// Screen screen = new Screen();
	public clickOnImage(String imageName) throws Exception {
		Match m = screen.find(getPattern(imageName));

Usage inside test cases
Note that when referencing images the path has to start with ‘/’ (fowardslash) to make sure the image is picked up correctly from within the artifact.

class Test {
	private static TestArtifact sikuli = new TestArtifact();
	public void shallClickImage() throws Exception {

Example of artifact pom

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">

    <name>Sikili wrapper test artifact</name>



WebDriver tricks of the trade

A post to be used as a reference for items/issues that has surfaced when using WebDriver with Java.


Muting WebDriver logs

At points where WebDriver is really verbose it is quite convenient to mute the output or at least certain levels of it.

// Java
// Set it before creating the WebDriver instance to avoid having any messages generated from the
// constructor call
RemoteWebDriver.setLogLevel(Level.WARNING); // java.util.logging.Level
WebDriver driver = new FirefoxDriver(profile);


Avoiding untrusted SSL cerificate errors when using Firefox

Typical test environment issue. A simple workaround that worked for us was to simply set the profile used to accept and assume any certificate issues.

// Java
FirefoxProfile profile = new FirefoxProfile();
WebDriver driver = new FirefoxDriver(profile);


Running FireFox in full screen

Especially handy when combining Sikuli and WebDriver, you need to be absolutely sure that as much as possible is visible on the screen.



Relative xpaths from the current WebElement

Very useful when working with complex HTML-pages whose elements are very deep down and can only be found using xpath. Maintaining these long xpaths in multiple places in the test code base is a pain. The solution is to do the xpathing in parts to minimize the effort needed to maintain the xpath-strings.

		  <td>cell to find</td><td></td>

Starting the xpath-string with the DOT is equivalent to starting the search from the current node.

WebElement tableElement = driver.findElement(By.xpath("//html/body/table"));
// Using relative xpath from the beginning of the table to find the first cell.
// Note that it has to start with the '.', DOT
WebElement cell = driver.findElement(By.xpath("./tbody/tr[1]/td[1]"));


Switching between open windows

Based on words in the page title.

Set<String> windows = driver.getWindowHandles();
for (String window : windows) {
  if (driver.getTitle().contains(pageTitle)) {


Dismissing/accepting alert dialog windows

Whenever an alert window pops-up it has to be accepted or dismissed to avoid blocking the test execution, this is simply handled using Alert class (Selenium docs).

// WebDriver driver = new FirefoxDriver();
Alert alert = driver.switchTo().alert();
// OR
// alert.dismiss();