Using junit @Rule, expectCause() and hamcrest matchers

Question

I have a test:

@Rule public ExpectedException thrown = ExpectedException.none(); ... @Test public void testMethod() {     final String error = "error message";     Throwable expectedCause = new IllegalStateException(error);     thrown.expectCause(org.hamcrest.Matchers.<Throwable>equalTo(expectedCause));     someServiceThatTrowsException.foo(); } 

When run via mvn the test method, I'm getting the error:

java.lang.NoSuchMethodError: org.junit.rules.ExpectedException.expectCause(Lorg/hamcrest/Matcher;)V

Test compiles fine.

Please help me, cannot understand how to test the cause of the exception?

Answer 1

Try it this way:

@Rule public ExpectedException thrown = ExpectedException.none();  @Test public void testMethod() throws Throwable {     final String error = "error message";     Throwable expectedCause = new IllegalStateException(error);     thrown.expectCause(IsEqual.equalTo(expectedCause));     throw new RuntimeException(expectedCause); } 

Consider not to check against the cause by equals but by IsInstanceOf and / or comapring the exception message if necessary. Comparing the cause by equals check the stacktrace as well, which may be more than you would like to test / check. Like this for example:

@Rule public ExpectedException thrown = ExpectedException.none();  @Test public void testMethod() throws Throwable {     final String error = "error message";     thrown.expectCause(IsInstanceOf.<Throwable>instanceOf(IllegalStateException.class));     thrown.expectMessage(error);     throw new RuntimeException(new IllegalStateException(error)); } 

Answer 2

A little bit more briefly with static imports and checking both the class and the message of the cause exception:

import static org.hamcrest.Matchers.allOf; import static org.hamcrest.Matchers.hasProperty; import static org.hamcrest.Matchers.instanceOf; import static org.hamcrest.Matchers.is; import static org.junit.Assert.assertThat;  @Test public void testThatThrowsNiceExceptionWithCauseAndMessages(){       expectedException.expect(RuntimeException.class );      expectedException.expectMessage("Exception message");                                                 expectedException.expectCause(allOf(instanceOf(IllegalStateException.class),                                         hasProperty("message", is("Cause message"))) );       throw new RuntimeException("Exception message", new IllegalStateException("Cause message")); } 

You could even use the hasProperty matcher to assert nested causes or to test the "getLocalizedMessage" method.