Resolved versions for app (26.1.0) and test app (27.1.1)

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.

错误原因：app 和test依赖冲突

原有app的build.gradle依赖：
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’
}
解决方案：
方案1：
implementation ‘com.android.support:appcompat-v7:26.1.0’ 改为implementation ‘com.android.support:appcompat-v7:27.1.1’ ，同时compileSdkVersion 26 改为compileSdkVersion 27

方案2：
androidTestImplementation ‘com.android.support.test:runner:1.0.2’
androidTestImplementation ‘com.android.support.test.espresso:espresso-core:3.0.2’
改为：
androidTestImplementation ‘com.android.support.test:runner:1.0.1’
androidTestImplementation ‘com.android.support.test.espresso:espresso-core:3.0.1’
重新编译