The JUnit runner will need to access the field reflectively to run the rule. If the field was private the access would throw IllegalAccessException. Another option would have been to have the runner modify the access from private to public before running the rule. However that could cause problems in case a security manager is … Read more
ExpectedException works by wrapping your entire test method in a try-catch block via a JUnit @Rule. When your code throws an exception, it goes up the stack to the nearest try/catch, which happens to be in the ExpectedException instance (which checks that it is the exception you’re expecting). In Java, if an uncaught exception occurs … Read more
In a general way, what you did with @Rule and @ClassRule in JUnit 4 should be done with @ExtendWith and Extension that associated provide a very close feature in JUnit 5. It works as standards JUnit lifecycle hooks but that it is extracted in a Extension class. And similarly to @Rule, as many Extensions as … Read more
Rules are used to add additional functionality which applies to all tests within a test class, but in a more generic way. For instance, ExternalResource executes code before and after a test method, without having to use @Before and @After. Using an ExternalResource rather than @Before and @After gives opportunities for better code reuse; the … Read more