Why Catching All Exceptions is Not a Good Idea

Oct 13, 2025 by magicalceylontours.com 135 views

Introduction

ErrorCollector and MultipleFailureException are incredibly useful tools in JUnit, but they feel only half integrated. ExternalResource and TestWatcher execute their functionality even if the test throws an exception, and if that functionality itself throws, then these accumulate the multiple exceptions into a MultipleFailureException. However, Verifier (and thus, almost all rules that extend it) does NOT run if the test throws a MultipleFailureException, which is a missed opportunity. This is especially ironic since ErrorCollector itself extends Verifier, so if a test has multiple ErrorCollector rules for any reason (inheritance or toolchain RuleChains), then only the innermost ErrorCollector collects errors. In this article, we will explore how Verifier and similar rules can be improved to validate if MultipleFailureException is thrown.

The Problem with Verifier

Verifier is a powerful tool in JUnit that allows developers to write custom rules for their tests. However, it has a limitation that prevents it from working seamlessly with ErrorCollector and MultipleFailureException. When a test throws a MultipleFailureException, Verifier does not run, which means that the post-test verification functionality is not executed. This is a missed opportunity, especially since ErrorCollector itself extends Verifier.

The Ideal Solution

The ideal solution would be to modify Verifier to wrap its base.evaluate(); call in a try/catch block. If it catches a MultipleFailureException, then it should execute .verify(). The MultipleFailureException exceptions should be accumulated and any new exception(s?) thrown by .verify() should be rethrown as a new MultipleFailureException.

Why Catching All Exceptions is Not a Good Idea

One possible solution could be to catch all exceptions and run .verify() and rethrow the original exception afterward. However, this approach has a significant drawback. If a test fails with a non-MultipleFailureException, running post-test-verification almost certainly doesn't make sense. It would virtually always fail, providing noise instead of value. Therefore, it is not proposed to execute it for any exception other than MultipleFailureException.

Why This Reasoning Only Applies to Exceptions Thrown from the Test Method Itself

It is worth noting that this reasoning only really applies to exceptions thrown from the test method itself. Ideally, we do want to run post-test-verification if inner Rules' tear-downs throw exceptions. However, usefully, existing JUnit rules only throw MultipleFailureException in teardown, so no additional work is needed.

Examining the JUnit-5 Code

It is worth noting that the author of this article has not yet examined the junit-5 code to see if this issue has already been fixed, if 5 has new class/method names, or if 5 rules now throw exceptions besides MultipleFailureException in teardown. However, it is understood and accepted that no new junit-4 releases are planned, and that if this feature is accepted, then the changes will probably only be implemented in junit-5.

Conclusion

In conclusion, Verifier and similar rules should be modified to validate if MultipleFailureException is thrown. This can be achieved by wrapping the base.evaluate(); call in a try/catch block and executing .verify() if a MultipleFailureException is caught. The MultipleFailureException exceptions should be accumulated and any new exception(s?) thrown by .verify() should be rethrown as a new MultipleFailureException. This will ensure that post-test verification is executed even if a test throws a MultipleFailureException, providing more value to developers.

Recommendations

Based on the analysis above, the following recommendations are made:

Modify Verifier to wrap its base.evaluate(); call in a try/catch block.
Execute .verify() if a MultipleFailureException is caught.
Accumulate the MultipleFailureException exceptions and any new exception(s?) thrown by .verify().
Rethrow the accumulated exceptions as a new MultipleFailureException.
Consider implementing this feature in junit-5.

Introduction

In our previous article, we discussed how Verifier and similar rules can be improved to validate if MultipleFailureException is thrown. In this article, we will answer some frequently asked questions related to this topic.

Q: Why is it important to validate if MultipleFailureException is thrown?

A: Validating if MultipleFailureException is thrown is important because it ensures that post-test verification is executed even if a test throws a MultipleFailureException. This provides more value to developers and helps to identify and fix issues more efficiently.

Q: What is the ideal solution for modifying Verifier to validate if MultipleFailureException is thrown?

A: The ideal solution is to modify Verifier to wrap its base.evaluate(); call in a try/catch block. If it catches a MultipleFailureException, then it should execute .verify(). The MultipleFailureException exceptions should be accumulated and any new exception(s?) thrown by .verify() should be rethrown as a new MultipleFailureException.

Q: Why is catching all exceptions not a good idea?

A: Catching all exceptions is not a good idea because it would virtually always fail, providing noise instead of value. If a test fails with a non-MultipleFailureException, running post-test-verification almost certainly doesn't make sense.

Q: Why does this reasoning only apply to exceptions thrown from the test method itself?

A: This reasoning only applies to exceptions thrown from the test method itself because ideally, we do want to run post-test-verification if inner Rules' tear-downs throw exceptions. However, usefully, existing JUnit rules only throw MultipleFailureException in teardown, so no additional work is needed.

Q: Has this issue been fixed in JUnit-5?

A: The author of this article has not yet examined the junit-5 code to see if this issue has already been fixed, if 5 has new class/method names, or if 5 rules now throw exceptions besides MultipleFailureException in teardown. However, it is understood and accepted that no new junit-4 releases are planned, and that if this feature is accepted, then the changes will probably only be implemented in junit-5.

Q: What are the recommendations for modifying Verifier to validate if MultipleFailureException is thrown?

A: The following recommendations are made:

Modify Verifier to wrap its base.evaluate(); call in a try/catch block.
Execute .verify() if a MultipleFailureException is caught.
Accumulate the MultipleFailureException exceptions and any new exception(s?) thrown by .verify().
Rethrow the accumulated exceptions as a new MultipleFailureException.
Consider implementing this feature in junit-5.

Q: What are the benefits of modifying Verifier to validate if MultipleFailureException is thrown?

A: The benefits of modifying Verifier to validate if MultipleFailureException is thrown include:

Ensuring that post-test verification is executed even if a test throws a MultipleFailureException.
Providing more value to developers and helping to identify and fix issues more efficiently.

Conclusion

In conclusion, validating if MultipleFailureException is thrown is an important aspect of improving Verifier and similar rules. By answering these frequently asked questions, we hope to provide more clarity and understanding on this topic.