Reattempting Failed JUnit Tests with a Retry Rule
JUnit tests can occasionally fail due to unexpected delays in the system under test. To mitigate such failures, you can employ a Retry Rule to give failing tests a second chance.
To implement a Retry Rule, create a custom rule by extending Rule. The apply() method will define the logic around the test, including the retry loop:
<code class="java">public class Retry implements TestRule { private int retryCount; public Retry(int retryCount) { this.retryCount = retryCount; } public Statement apply(Statement base, Description description) { return statement(base, description); } private Statement statement(final Statement base, final Description description) { return new Statement() { @Override public void evaluate() throws Throwable { Throwable caughtThrowable = null; // Retry loop for (int i = 0; i < retryCount; i++) { try { base.evaluate(); return; } catch (Throwable t) { caughtThrowable = t; System.err.println(description.getDisplayName() + ": run " + (i+1) + " failed"); } } System.err.println(description.getDisplayName() + ": giving up after " + retryCount + " failures"); throw caughtThrowable; } }; } }</code>
Apply the Retry Rule to your test case using @Rule:
<code class="java">public class RetryTest { @Rule public Retry retry = new Retry(3); // Test methods... }</code>
Using a Custom TestRunner
Alternatively, you can create a custom TestRunner that extends BlockJUnit4ClassRunner and overrides the runChild() method to include retry logic. This method overrides how individual test methods are run.
Conclusion
By using a Retry Rule or a custom TestRunner, you can enhance your JUnit tests to handle temporary failures and ensure test reliability even in demanding conditions.
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