λ... < ユニットテストのテストコード上で Retrolambda が使えない ref: http://qiita.com/eccyan/items/400a60da44d1d603380b

build.gradle

tasks.withType(Test) {
    project.tasks
            .findAll { task -> (task.name ==~ /compileTest.*Java/) }
            .each { task ->
        task.doFirst {
            def buildPath = "$project.buildDir/retrolambda"
            def jarPath = "$buildPath/$project.android.compileSdkVersion"
            def javac = "${project.retrolambda.tryGetJdk()}/bin/javac"

            sourceCompatibility = JavaVersion.VERSION_1_8
            targetCompatibility = JavaVersion.VERSION_1_8

            options.fork = true
            options.compilerArgs += ["-bootclasspath", "$jarPath/android.jar"]
            options.forkOptions.executable = javac
        }
    }
}

file0.txt

Test.java:61: error: illegal start of expression
  .filter(state -> state != State.UNINITIALIZED)

file1.txt

An exception has occurred in the compiler (1.8.0_25). Please file a bug at the Java Developer Connection (http://java.sun.com/webapps/bugreport)  after checking the Bug Parade for duplicates. Include your program and the following diagnostic in your report.  Thank you.
com.sun.tools.javac.code.Symbol$CompletionFailure: class file for java.lang.invoke.MethodType not found

file2.txt

23:14:30.815 [DEBUG] [org.gradle.api.internal.tasks.compile.NormalizingJavaCompiler] Compiler arguments: -d /app/build/test-classes/debug -g -encoding UTF-8 -bootclasspath /Applications/android-sdk/platforms/android-21/android.jar -classpath 
...

file4.txt

Test > initializationError FAILED
    java.lang.UnsupportedClassVersionError