How Can I Efficiently Assert Exceptions in JUnit Tests?

Asserting Exceptions in JUnit Tests

Traditionally, testing for exceptions in JUnit involved verbose try-catch blocks as exemplified in the provided code. However, several alternatives exist that streamline this process.

JUnit 5 and 4.13

Since JUnit 4.13, the @Test(expected = IndexOutOfBoundsException.class) annotation can be used to assert that a specific exception is thrown during the execution of the annotated method. For example:

@Test(expected = IndexOutOfBoundsException.class)
public void testIndexOutOfBoundsException() {

    ArrayList emptyList = new ArrayList();
    Object o = emptyList.get(0);

}

AssertJ and Google Truth

AssertJ and Google Truth are popular assertion libraries that provide more readable and expressive assertions, including ones for testing exceptions. For instance, with AssertJ:

import static org.assertj.core.api.Assertions.assertThatThrownBy;

@Test
public void testIndexOfBoundsException() {

    ArrayList emptyList = new ArrayList();
    assertThatThrownBy(() -> emptyList.get(0)).isInstanceOf(IndexOutOfBoundsException.class);

}

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