How do I assert my exception message with JUnit Test annotation

Question

I have written a few JUnit tests with  Test annotation  If my test method throws a checked exception and if I want to assert the message along with the exception  is there a way to do so with JUnit  Test annotation  AFAIK  JUnit 4 7 doesn t provide this feature but does any future versions provide it  I know in  NET you can assert the message and the exception class  Looking for similar feature in the Java world   This is what I want    Test  expected   RuntimeException class  message    Employee ID is null   public void shouldThrowRuntimeExceptionWhenEmployeeIDisNull

User · Accepted Answer

You could use the  Rule annotation with ExpectedException  like this    Rule public ExpectedException expectedEx   ExpectedException none      Test public void shouldThrowRuntimeExceptionWhenEmployeeIDisNull   throws Exception       expectedEx expect RuntimeException class       expectedEx expectMessage  Employee ID is null            do something that should throw the exception        System out println         Starting Exception process               throw new NullPointerException  Employee ID is null        Note that the example in the ExpectedException docs is  currently  wrong - there s no public constructor  so you have to use ExpectedException none

User · Answer

If using  Rule  the exception set is applied to all the test methods in the Test class

User · Answer

I like the  Rule answer  However  if for some reason you don t want to use rules  There is a third option    Test  expected   RuntimeException class  public void myTestMethod        try              Run exception throwing operation here         catch RuntimeException re             String message    Employee ID is null         assertEquals message  re getMessage           throw re            fail  Employee Id Null exception did not throw

User · Answer

In JUnit 4 13 you can do   import static org junit Assert assertEquals  import static org junit Assert assertThrows         Test void exceptionTesting       IllegalArgumentException exception   assertThrows      IllegalArgumentException class          - gt    throw new IllegalArgumentException  a message              assertEquals  a message   exception getMessage         This also works in JUnit 5 but with different imports   import static org junit jupiter api Assertions assertEquals  import static org junit jupiter api Assertions assertThrows

User · Answer

I would prefer AssertJ for this          assertThatExceptionOfType ExpectedException class           isThrownBy    - gt                   method call            withMessage  quot My message quot

User · Answer

Test  expectedExceptions   ValidationException class  expectedExceptionsMessageRegExp    This is not allowed   public void testInvalidValidation   throws Exception         test code

User · Answer

Actually  the best usage is with try catch  Why  Because you can control the place where you expect the exception   Consider this example    Test  expected   RuntimeException class  public void someTest           test preparation       actual test     What if one day the code is modified and test preparation will throw a RuntimeException  In that case actual test is not even tested and even if it doesn t throw any exception the test will pass   That is why it is much better to use try catch than to rely on the annotation

User · Answer

Raystorm had a good answer   I m not a big fan of Rules either   I do something similar  except that I create the following utility class to help readability and usability  which is one of the big plus es of annotations in the first place     Add this utility class   import org junit Assert   public abstract class ExpectedRuntimeExceptionAsserter        private String expectedExceptionMessage       public ExpectedRuntimeExceptionAsserter String expectedExceptionMessage            this expectedExceptionMessage   expectedExceptionMessage             public final void run            try              expectException                Assert fail String format  Expected a RuntimeException   s    expectedExceptionMessage              catch  RuntimeException e               Assert assertEquals  RuntimeException caught  but unexpected message   expectedExceptionMessage  e getMessage                          protected abstract void expectException         Then for my unit test  all I need is this code    Test public void verifyAnonymousUserCantAccessPrivilegedResourceTest        new ExpectedRuntimeExceptionAsserter  anonymous user can t access privileged resource             Override         protected void expectException                 throw new RuntimeException  anonymous user can t access privileged resource                    run      passes test  expected exception is caught  and this  Test returns normally as  Passed

User · Answer

I like user64141 s answer but found that it could be more generalized  Here s my take   public abstract class ExpectedThrowableAsserter implements Runnable        private final Class lt   extends Throwable gt  throwableClass      private final String expectedExceptionMessage       protected ExpectedThrowableAsserter Class lt   extends Throwable gt  throwableClass  String expectedExceptionMessage            this throwableClass   throwableClass          this expectedExceptionMessage   expectedExceptionMessage             public final void run             try               expectException              catch  Throwable e                assertTrue String format  Caught unexpected  s   e getClass   getSimpleName     throwableClass isInstance e                assertEquals String format   s caught  but unexpected message   throwableClass getSimpleName     expectedExceptionMessage  e getMessage                 return                    fail String format  Expected  s  but no exception was thrown    throwableClass getSimpleName                 protected abstract void expectException         Note that leaving the  fail  statement within the try block causes the related assertion exception to be caught  using return within the catch statement prevents this

User · Answer

I never liked the way of asserting exceptions with Junit  If I use the  expected  in the annotation  seems from my point of view we re violating the  given  when  then  pattern because the  then  is placed at the top of the test definition   Also  if we use   Rule   we have to deal with so much boilerplate code  So  if you can install new libraries for your tests  I d suggest to have a look to the AssertJ  that library now comes with SpringBoot   Then a test which is not violating the  given when then  principles  and it is done using AssertJ to verify   1 - The exception is what we re expecting  2 - It has also an expected message  Will look like this     Test void should throwIllegalUse when idNotGiven            when     final Throwable raisedException   catchThrowable    - gt  getUserDAO byId null           then     assertThat raisedException  isInstanceOf IllegalArgumentException class               hasMessageContaining  Id to fetch is mandatory

User · Answer

Import the catch-exception library  and use that  It s much cleaner than the ExpectedException rule or a try-catch   Example form their docs   import static com googlecode catchexception CatchException    import static com googlecode catchexception apis CatchExceptionHamcrestMatchers        given  an empty list List myList   new ArrayList        when  we try to get the first element of the list catchException myList  get 1       then  we expect an IndexOutOfBoundsException with message  Index  1  Size  0  assertThat caughtException      allOf      instanceOf IndexOutOfBoundsException class       hasMessage  Index  1  Size  0        hasNoCause

User · Answer

Do you have to use  Test expected SomeException class   When we have to assert the actual message of the exception  this is what we do    Test public void myTestMethod       try         final Integer employeeId   null      new Employee employeeId       fail  Should have thrown SomeException but did not           catch  final SomeException e           final String msg    Employee ID is null       assertEquals msg  e getMessage

[java] How do I assert my exception message with JUnit Test annotation?

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