You’ve probably got one of two problems:
1) You’re using JUnit 4.11, which doesn’t include hamcrest. Add the hamcrest 1.3 library to your classpath.
2) You’ve got hamcrest 1.3 on your classpath, but you’ve got another version of either junit or hamcrest on your classpath.
For background, junit pre 4.11 included a cut down version of hamcrest 1.1. 4.11 removed these classes.