I solved this jar hell problem in my Gradle project with the code below:
testCompile (group: 'junit', name: 'junit', version: '4+') {
exclude group: 'org.hamcrest'
}
testCompile ('org.mockito:mockito-core:1+') {
exclude group: 'org.hamcrest'
}
testCompile 'org.hamcrest:java-hamcrest:2.0.0.0'