Best way to check whether a certain exception type was the cause (of a cause, etc …) in a nested exception?

Question

I am writing some JUnit tests that verify that an exception of type MyCustomException is thrown. However, this exception is wrapped in other exceptions a number of

Answer 1

If you are using Apache Commons Lang, then you can use the following:

(1) When the cause should be exactly of the specified type

if (ExceptionUtils.indexOfThrowable(exception, ExpectedException.class) != -1) {
    // exception is or has a cause of type ExpectedException.class
}

(2) When the cause should be either of the specified type or its subclass type

if (ExceptionUtils.indexOfType(exception, ExpectedException.class) != -1) {
    // exception is or has a cause of type ExpectedException.class or its subclass
}