I tried to add some simple Junit to my AndroidStudio project following the Android Tools Project Site - Unit Test Guide.
I created the /src/test/java folder and wrote my simple unit test, finally  I added to the build.gradle file 
dependencies {
  testCompile 'junit:junit:4.12'
}
The problem is that when I run the test I got build error since the compiler could not find the org.junit.Test import.
The only solution that I found is to change the dependencies line using 
provided instead of testCompile .
This is the complete gradle.build
buildscript {
    repositories {
        mavenCentral()
    }
    dependencies {
        classpath 'com.android.tools.build:gradle:1.3.0'
    }
}
apply plugin: 'com.android.application'
repositories {
    mavenCentral()
}
dependencies {
    compile fileTree(include: '*.jar', dir: 'libs')
    compile project(':Proj1')
    compile project(':Proj2')
    compile project(':Proj3')
    provided 'junit:junit:4.12'
}
android {
    compileSdkVersion 19
    buildToolsVersion "23.0.1"
    lintOptions {
        disable 'InvalidPackage'
    }
    sourceSets {
        main {
            manifest.srcFile 'AndroidManifest.xml'
            java.srcDirs = ['src']
            resources.srcDirs = ['src']
            aidl.srcDirs = ['src']
            renderscript.srcDirs = ['src']
            res.srcDirs = ['res']
            assets.srcDirs = ['assets']
        }
        // by a similar customization.
        debug.setRoot('build-types/debug')
        release.setRoot('build-types/release')
    }
....
}
What did I do wrong?