Error:Execution failed for task ':app:preDebugAndroidTestBuild'.

> 
> Conflict with dependency 'com.android.support:support-annotations' in project ':app'. Resolved versions for app (26.1.0) and test app (27.1.1) differ. See <https://d.android.com/r/tools/test-apk-dependency-conflicts.html> for details.
> 
> 
> 

**Edit: Following is taken from the comments**

Following are my dependencies:

```
dependencies { 
    implementation fileTree(dir: 'libs', include: ['*.jar']) 
    implementation 'com.android.support:appcompat-v7:26.1.0' 
    implementation 'com.android.support.constraint:constraint-layout:1.1.0' 
    testImplementation 'junit:junit:4.12' 
    androidTestImplementation 'com.android.support.test:runner:1.0.2' 
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2' 
    androidTestImplementation 'com.android.support:support-annotations:27.1.1' 
}

```