Adding custom messages to TestNG failures

Question

I'm in the process of migrating a test framework from JUnit to TestNG. This framework is used to perform large end-to-end integration tests with Selenium that take several minutes to run and consist of several hundred steps across dozens of browser pages.

DISCLAIMER: I understand that this makes unit testing idealists very uneasy, but this sort of testing is required at most large service oriented companies and using unit testing tools to manage these integration tests is currently the most widespread solution. It wasn't my decision. It's what I've been asked to work on and I'm attempting to make the best of it.

At any rate, these tests fail very frequently (surprise) and making them easy to debug is of high importance. For this reason we like to detect test failures before they're reported, append some information about the failure, and then allow JUnit to fail with this extra information. For instance, without this information a failure may look like:

java.lang.<'SomeObscureException'>: <'Some obscure message'> at <'StackTrace'>

But with the added information it will look like:

java.lang.AssertionError:
Reproduction Seed: <'Random number used to generate test case'>
Country: <'Country for which test was set to run'>
Language: <'Localized language used by test'>
Step: <'Test step where the exception occurred'>
Exception Message: <'Message explaining probable cause of failure'>
Associated Exception Type: <'SomeObscureException'>
Associated Exception Message: <'Some obscure message'>
Associated Exception StackTrace: <'StackTrace'>
Exception StackTrace: <'StackTrace where we appended this information'>

It's important to note that we add this information before the test actually fails. Because our reporting tool is based entirely on the exceptions thrown by JUnit this ensures that the information we need is present in those exceptions. Ideally I'd like to add this information to an HTML or XML document using a reporter class after the test fails but before teardown is performed and then modify our reporting tool to pick up this extra information and append it to our e-mail reports. However, this has been a hard sell at our sprint planning meetings and I have not been allotted any time to work on it (running endless regressions for the developers is given higher priority than working on the test framework itself. Such is the life of the modern SDET). I also believe strongly in balance and refuse to cut into other parts of my life to get this done outside of tracked time.

What we're currently doing is this:

public class SomeTests extends TestBase {

    @Test
    public void someTest() {
        // Test code
    }

    // More tests
}

public abstract class TestBase {

    @Rule
    public MyWatcher watcher = new MyWatcher();

    // More rules and variables

    @Before
    public final void setup() {
        // Read config, generate test data, create Selenium WebDriver, etc.
        // Send references to all test objects to MyWatcher
    }
}

public class MyWatcher extends TestWatcher {

    // Test object references

    @Override
    public void failed(Throwable throwable, Description description) {
        StringBuilder sb = new StringBuilder();

        // Append custom test information to sb.

        String exceptionSummary = sb.toString();
        Assert.fail(exceptionSummary);
    }

    @Override
    public void finished(Description description) {
        // Shut down Selenium WebDriver, kill proxy server, etc.
    }

    // Miscellaneous teardown and logging methods
}

1. JUnit starts.
2. SomeTests inherits from TestBase class. TestBase instantiates our own instance of a TestWatcher via @Rule annotation (MyWatcher).
3. Test setup is run in TestBase class.
4. References to test objects are sent to MyWatcher.
5. JUnit begins someTest() method.
6. someTest fails at some point.
7. JUnit calls overridden failed() method in MyWatcher.
8. failed() method appends custom test information to new message using references passed by TestBase.
9. failed() method calls JUnit's Assert.fail() method with the customized message.
10. JUnit throws a java.lang.Assertion error for this new failure with the customized message. This is the exception that actually gets recorded in the test results.
11. JUnit calls overridden finished() method.
12. finished() method performs test teardown.
13. Our reporting tool picks up the summarized errors thrown by JUnit, and includes them in the e-mails we receive. This makes life easier than debugging the original exceptions would be without any of the extra information added by MyWatcher after the original failure.

I'd now like to implement a similar mechanism using TestNG. I first tried adding an IInvokedMethodListener in a @Listener annotation to our TestBase class as a way of replacing the TestWatcher that we were using in JUnit. Unfortunately the methods in this listener were getting called after every @BeforeMethod and @AfterMethod call as well as for the actual tests. This was causing quite a mess when I called Assert.fail from inside the IInvokedMethodListener so I opted to scrap this approach and insert the code directly into an @AfterMethod call in our TestBase class.

Unfortunately TestNG does not appear to handle the 'failing twice' approach that we were using in JUnit. When I call Assert.fail in the @AfterMethod of a test that has already failed it gets reported as an additional failure. It seems like we're going to have to come up with another way of doing this until I can get authorization to write a proper test reporter that includes the information we need for debugging.

In the meantime, we still need to dress up the exceptions that get thrown by TestNG so that the debugging information will appear in our e-mail reports. One idea I have for doing this is to wrap every single test in a try/catch block. If the test fails (an exception gets thrown), then we can catch that exception, dress it up in a summary exception with the debugging information added to that exception's message, and call Assert.fail with our new summarized exception. That way TestNG only ever sees that one exception and should only report one failure. This feels like a kludge on top of a kludge though, and I can't help but feel that there's a better way of doing this.

Does anybody know of a better method for modifying what gets reported by TestNG? Is there some kind of trick I can use for replacing the original exception with my own using ITestContext or ITestResult? Can I dive in somewhere and remove the original failure from some list, or is it already too late to stop TestNG's internal reporting by the time I get to the @AfterMethod functions?

Do you have any other advice regarding this sort of testing or exception handling in general? I don't have many knowledgeable co-workers to help with this stuff so I'm pretty much just winging it.

Answer 1

Implement IInvokedMethodListener:

public class InvokedMethodListener implements IInvokedMethodListener {
    @Override
    public void beforeInvocation(IInvokedMethod method, ITestResult testResult) {
    }

    @Override
    public void afterInvocation(IInvokedMethod method, ITestResult result) {
        if (method.isTestMethod() && ITestResult.FAILURE == result.getStatus()) {
            Throwable throwable = result.getThrowable();
            String originalMessage = throwable.getMessage();
            String newMessage = originalMessage + "\nReproduction Seed: ...\nCountry: ...";
            try {
                FieldUtils.writeField(throwable, "detailMessage", newMessage, true);
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }
}

Register it in your test:

@Listeners(InvokedMethodListener.class)
public class YourTest {
    @Test
    public void test() {
        Assert.fail("some message");
    }
}

or in testng.xml.

If you execute it, you should get:

java.lang.AssertionError: some message
Reproduction Seed: ...
Country: ...

Answer 2

You can user SoftAssert Class in testNG for implementing above scenario. SoftAssert Class has an hash map array which stores all the error message from Asserts in test cases and prints them in the end of the test case. you can also extend Assertion class to implement methods as per your requirement.

More information regarding SoftAssert class and its implementation can be found here