There is nothing worse than being reported that UI test failed but without clear evidence what exactly went wrong. And what could be better evidence than screenshot just after the failure?

This is a second post about Geb in a short time. This time we will learn how to configure Geb to take a screenshot every time our UI test fails. Image of page at the moment when test failed is often very helpful in debugging mysteriously failing UI test on CI server and can save a lot of time when trying to solve such problems.

The Problem

We need a simple way to configure Geb UI tests to take a screenshot on each test fail. This should be “add and forget” config that does not need any changes when we add more tests to our application.

Solution

We have to find some type of listener that waits for different test results and fires proper method when test fails. In TestNG we have a TestListenerAdapter so probably Geb or Spock should have something similar.

After some digging I was able to locate IRunListener with method I need:

Simple version of test failure listener
Luckily this interface comes with abstract class named AbstractRunListener that allows us to implement only methods we want instead of fulfilling the whole contract specified by IRunListener.

So our first step will be to print something to the console every time our test fails:

Adding custom listener to all tests with Spock extension
But except implementation of a listener, we have to add this listener to our tests. Currently in Spock this is possible only with extensions. Again, I had to find proper extension to use and ended with interface IGlobalExtension which has only one method visiting each spec (test method) in our codebase:

So extension implementation looks as follows, to each visited spec we add our TakeScreenshotOnTestFailureListener listener:

Registering Spock global extension

Each global extension have to be registered to Spock. This can be achieved by placing text file with easy to remember name in META-INF/services directory. File must be named org.spockframework.runtime.extension.IGlobalExtension and should contain full name of our implementation of IGlobalExtension interface:

Taking a screenshot on each UI test fail
Now on each test fail we will see that our text message is printed to the console. This proves that our solution is going in the right direction and last thing still not implemented is taking a screenshot.

Taking a screenshot using Selenium driver is quite easy, it is one method call, but before that we have to acquire driver instance in our listener class. Directly it is impossible to access driver directly from the listener so we need to store it in globally accessible object. Simplest solution is to save reference to the driver when we create it in our GebConfig file. So let’s create a singleton that will hold our browser:

and initialise it in GebConfig.groovy script located in root package of our project:

Now we can access driver from our listener object, so final taking screenshot logic is pretty straightforward:

And that’s all. Each failed test will now appear with corresponding screenshot from browser.

 

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