How Can I Give Failing JUnit Tests a Second Chance to Pass?

Running Failed JUnit Tests for a Second Chance

In JUnit, it is possible to configure tests to have a second chance to pass when they fail initially. This can be particularly useful for tests that may fail intermittently due to external factors, such as network issues or slow server responses. Here are two methods to achieve this:

Using a TestRule

A TestRule allows you to define custom logic to be executed before and after each test method. To create a TestRule for retrying failed tests:

<code class="java">public class RetryTestRule implements TestRule {

    private int retryCount;

    public RetryTestRule(int retryCount) {
        this.retryCount = retryCount;
    }

    @Override
    public Statement apply(Statement base, Description description) {
        return new Statement() {
            @Override
            public void evaluate() throws Throwable {
                Throwable caughtThrowable = null;
                for (int i = 0; i < retryCount; i++) {
                    try {
                        base.evaluate();
                        return;
                    } catch (Throwable t) {
                        caughtThrowable = t;
                    }
                }
                throw caughtThrowable;
            }
        };
    }
}

In your test class, apply the rule to the desired tests:

<code class="java">@Rule
public RetryTestRule retry = new RetryTestRule(3);

Using a Custom TestRunner

Alternatively, you can define a custom TestRunner that overrides the runChild() method to control how each test method is executed:

<code class="java">public class RetryTestRunner extends BlockJUnit4ClassRunner {
    private int retryCount;

    public RetryTestRunner(Class<?> testClass) {
        super(testClass);
        Annotation annotation = AnnotationUtils.getAnnotation(testClass, Retry.class);
        if (annotation != null) {
            retryCount = ((Retry) annotation).value();
        }
    }

    @Override
    protected void runChild(FrameworkMethod method, RunNotifier notifier) {
        for (int i = 0; i < retryCount; i++) {
            try {
                super.runChild(method, notifier);
                return;
            } catch (Throwable t) {
                if (i == retryCount - 1) {
                    throw t;
                }                
            }
        }
    }
}</code>

In your test class, use the custom TestRunner with @RunWith:

<code class="java">@RunWith(RetryTestRunner.class)
@Retry(3)
public class MyTestClass {}</code>

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