Dependency conflict error in my Android app which has Android Tests

I'm using AndroidStudio and Gradle to build my Android app with tests in the 'androidTest' source directory. I added a new dependency and am now getting the following issue when running Android Tests either AndroidStudio or './gradlew connectedCheck'. What's the preferred way to resolve this?

'Warning:Conflict with dependency 'org.somelibrary:library-core'. Resolved versions for app and test app differ.'