title: Gradle: conflict with dependencies
body: <p>I am following an online course on Android Development but I am stuck at the very beginning since I get a dependcy issue with Gradle which prevents me from successfully building example projects.
  The error is the famous:</p>
  
  <pre><code>Execution failed for task ':app:preDebugAndroidTestBuild'.
  &gt; 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.
  </code></pre>
  
  <p>My Gradle is below:</p>
  
  <pre><code>// Top-level build file where you can add configuration options common to all sub-projects/modules.
  
  buildscript {
  
      repositories {
          google()
          jcenter()
      }
      dependencies {
          classpath 'com.android.tools.build:gradle:3.0.1'
  
  
          // NOTE: Do not place your application dependencies here; they belong
          // in the individual module build.gradle files
      }
  }
  
  allprojects {
      repositories {
          google()
          jcenter()
      }
  }
  
  task clean(type: Delete) {
      delete rootProject.buildDir
  }
  </code></pre>
  
  <p>As suggested by the lecturer, I am using AS 3.0.1. However, the lecturer has not been able to solve this issue for me and since I am totally new with AS I have no idea how to proceed.</p>
  
  <p>Any help would be appreciated!</p>
  
  <p>Many thanks,
  Alberto</p>