Conflict with dependency 'com.android.support:support-media-compat' in project ':app'

When I try to start a test I get this error:

Conflict with dependency 'com.android.support:support-media-compat' in project ':app'. Resolved versions for app (27.0.0) and test app (27.1.1) differ. See https://d.android.com/r/tools/test-apk-dependency-conflicts.html for details.

and here's my build.gradle dependencies:

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:cardview-v7:27.1.1'
    implementation 'com.android.support:appcompat-v7:27.1.1'
    implementation 'com.android.support:recyclerview-v7:27.1.1'
    implementation 'com.android.support.constraint:constraint-layout:1.1.2'

    // ViewModel and LiveData
    implementation "android.arch.lifecycle:extensions:1.1.1"
    annotationProcessor "android.arch.lifecycle:compiler:1.1.1"
    // ButterKnife Library
    implementation 'com.jakewharton:butterknife:8.8.1'
    annotationProcessor 'com.jakewharton:butterknife-compiler:8.8.1'
    // Gson Library
    implementation 'com.google.code.gson:gson:2.8.5'
    // Glide Library
    implementation 'com.github.bumptech.glide:glide:4.8.0'
    annotationProcessor 'com.github.bumptech.glide:compiler:4.8.0'
    // ExoPlayer Library
    implementation 'com.google.android.exoplayer:exoplayer-core:2.8.3'
    implementation 'com.google.android.exoplayer:exoplayer-ui:2.8.3'

    testImplementation 'junit:junit:4.12'
    androidTestImplementation "com.android.support.test:rules:1.0.2"
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support:support-annotations:27.1.1'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-contrib:3.0.2'
}

I don't see using the version 27.0.0 anywhere in my code, and I think that ExoPlayer might be using that version internally! What can I possibly do to solve the conflict?!