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.

apply plugin: 'com.android.application'

android {

    compileSdkVersion 26//

    defaultConfig {

        applicationId "com.example.yueli.flightcheck"

        minSdkVersion 14

        targetSdkVersion 26//

        versionCode 1

        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

    }

    buildTypes {

        release {

            minifyEnabled false

            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'

        }

    }

}

dependencies {

    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'com.android.support:appcompat-v7:26.1.0'//：27.1.1

    implementation 'com.android.support.constraint:constraint-layout:1.1.2'

    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'

}

apply plugin: 'com.android.application'

android {

    compileSdkVersion 26

    defaultConfig {

        applicationId "com.example.yueli.flightcheck"

        minSdkVersion 14

        targetSdkVersion 26

        versionCode 1

        versionName "1.0"

        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

    }

    buildTypes {

        release {

            minifyEnabled false

            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'

        }

    }

}

dependencies {

    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'com.android.support:appcompat-v7:26.1.0'

    implementation 'com.android.support.constraint:constraint-layout:1.1.2'

    testImplementation 'junit:junit:4.12'

    androidTestImplementation 'com.android.support.test:runner:1.0.2'//1.0.1

    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'//3.0.1

}