I am trying to use Mockito in my Android project. I have found very nice tutorial that deals with it: http://www.paulbutcher.com/2012/05/mockito-on-android-step-by-step/
From @rjath's comment of @MrChaz's answer, this works better for me:
System.setProperty( "dexmaker.dexcache", getInstrumentation().getTargetContext().getCacheDir().getPath());
I put it in my setUp() method.
setUp()