In this example, we take a look at a JUnit example of failing a test on NullPointerException.
Code Example:
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertThrows;
import static org.junit.jupiter.api.Assertions.fail;
public class JunitExceptionExample {
@Test
public void test() {
try {
String str = null;
str.toLowerCase();
} catch (NullPointerException nullPointerException) {
assertThrows(NullPointerException.class, () -> {
throw nullPointerException;
});
} catch (Exception exception) {
fail("Expected NullPointerException, but caught: " + exception.getClass().getSimpleName());
}
}
}
In the above example, we have made use of the assertThrows method from org.junit.jupiter.api.Assertions class of Junit 5.
For this example: The method asserts that execution of the supplied executable throws an exception of the expectedType (NullPointerException) and returns the exception. If there is no exception thrown by your code, or a different expectation other than NullPointerException is thrown assertThrows method will fail.
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