問題報錯：

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.

問題分析：

com.android.support:support-annotations:[email protected] 和 com.android.support:support-annotations:[email protected]衝突

解決：

在app下的build.gradle檔案中的dependences {}中新增如下程式碼

androidTestCompile('com.android.support:support-annotations:26.1.0') {
    force = true
}