Custom hamcrest matcher in unit tests

Question

Having trouble implementing custom hamcrest matcher to use in Grails. Running the tests using my matcher fails with:

java.lang.NoSuchMethodError: org.hamcrest.Matcher.describeMismatch(Ljava/lang/Object;Lorg/hamcrest/Description;)V

After a bit of googling it seems that this is caused by the order of the loaded libraries: JUnit and Hamcrest. I have added the following dependency to my BuildConfig.groovy:

dependencies {
  test 'org.hamcrest:hamcrest-all:1.3'
}

Accordingly to instructions I was able to found, this could be fixed by making sure that hamcrest classes are loaded before JUnit ones. I do not know how to achieve this in Grails though or how to solve this in any other way.

Using Grails 2.2.1

Answer 1

This depends on the version of JUnit you're using. You can check this by looking in lib/junit/junit/jars. I think this is 4.10 by default. If so, please upgrade to 4.11. You can do this by explictly specifying it in the BuildConfig.groovy I believe:

dependencies {
  test 'junit:junit:4.11'
  test 'org.hamcrest:hamcrest-all:1.3'
}

For an explanation, before 4.11 a version of the hamcrest libraries were included in the JUnit distribution. This is no longer the case with 4.11, and you sometimes get a mismatch between class versions.