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JUnit Tip: Verifying that an Exception with a Particular Message was Thrown

 2 years ago
source link: https://blog.jakubholy.net/2011/09/16/junit-tip-verifying-that-an-exception-with-a-particular-message-was-thrown/
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JUnit Tip: Verifying that an Exception with a Particular Message was Thrown

September 16, 2011
JUnit has a hidden treasure which makes it easy to do something we have long longed for - namely not only to verify that an exception of a particular type has been thrown but also that its message contains the expected message. The hidden pearl is the @Rule ExpectedException and its JavaDoc documents well how to use it (slightly modified):

import org.junit.*;
import org.junit.rules.ExpectedException;

public static class HasExpectedException {
        @Rule
        public ExpectedException thrown= ExpectedException.none();

@Test
        public void throwsNothing() {
            // no exception expected, none thrown: passes.
        }

@Test
        public void throwsNullPointerExceptionWithMessage() {
                thrown.expect(NullPointerException.class);
                thrown.expectMessage("What happened here?");
                thrown.expectMessage(allOf(containsString("What"), containsString("here")));
                throw new NullPointerException("What happened here?");
        }
 }


(As you might have noticed, it uses Hamcrest matchers; containsString isn't included directly in junit and thus you'd need junit-dep + hamcrest jars.)
Tags: testing

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