Ehcache comes with a comprehensive JUnit test suite, which not only tests the code, but shows you how to use the Ehcache API.

You can browse the available tests here: https://fisheye.terracotta.org/browse/Ehcache_Documentation_Set/branches/ehcache-2.10.1/ehcache-core/src/test/java/net/sf/Ehcache_Documentation_Set/search. The unit tests are also available in the src.zip in the Ehcache tarball.