Classy Data v1.3.2+ uses Robolectric 3.1.2 which supports testing of applications at APL levels 16 to 23. Classy Data "out of the box" targets API level 23. For API levels 24 and above, you can get Robolectric to emulate the API level 23 SDK version by using @Config annotation in package org.robolectric.annotation. eg.

    @RunWith(RobolectricTestRunner.class)
    @Config(sdk = 23, application = TestClassyFyApplication.class)
    public class MainActivityTest

To change to a different API Level requires adjusting head pom.xml parameters robolectric.platform.version and robolectric.all.version. The possible values for the latter are given in the comments where these parameters are set.