I don't recall specifically how to make this fail with gremlin-test, but I did run into it at one point when writing a graph implementation. This blog describes the issue and workaround. https://tedvinke.wordpress.com/2013/12/17/mixing-junit-hamcrest-and-mockito-explaining-nosuchmethoderror/
The error trace looks like this:
There is a dependency conflict created by an older version of hamcrest coming out of mockito-all. The fix is to use mockito-core instead.
I'll submit a patch for this.