JUnit 5: How to assert an exception is thrown?

Question

Is there a better way to assert that a method throws an exception in JUnit 5?

Currently, I have to use an @Rule in order to verify that my test throws an exception, but this doesn't work for the cases where I expect multiple methods to throw exceptions in my test.

Answer 1

You can use assertThrows(), which allows you to test multiple exceptions within the same test. With support for lambdas in Java 8, this is probably going to become the canonical way to test for exceptions in JUnit.

Per the JUnit docs:

import static org.junit.jupiter.api.Assertions.assertThrows;

...

@Test
void exceptionTesting() {
    Executable closureContainingCodeToTest = () -> throw new IllegalArgumentException("a message");

    assertThrows(IllegalArgumentException.class, closureContainingCodeToTest, "a message");
}

Answer 2

Here is an easy way.

@Test
void exceptionTest() {

   try{
        model.someMethod("invalidInput");
        fail("Exception Expected!");
   }
   catch(SpecificException e){

        assertTrue(true);
   }
   catch(Exception e){
        fail("wrong exception thrown");
   }

}

It only succeeds when the Exception you expect is thrown.