Kotlinのテストで@rule

build.gradle

dependencies {
    testCompile 'junit:junit:4.12'

    androidTestCompile 'com.android.support:support-annotations:23.0.1'
    androidTestCompile 'com.android.support.test:runner:0.4'
    androidTestCompile 'com.android.support.test:rules:0.4'
    androidTestCompile 'com.android.support.test.uiautomator:uiautomator-v18:2.1.1'
    androidTestCompile 'com.squareup.assertj:assertj-android:1.1.0'
}

MainActivityTest.kt

package com.nagopy.android.aplin

import android.support.test.rule.ActivityTestRule
import android.support.test.runner.AndroidJUnit4
import android.widget.TextView
import org.assertj.android.api.Assertions
import org.junit.Rule
import org.junit.Test
import org.junit.runner.RunWith

@RunWith(AndroidJUnit4::class)
class MainActivityTest {

/*
    @Rule
    public val rule: ActivityTestRule<MainActivity> = ActivityTestRule(MainActivity::class.java)
    って書くと
    The @Rule 'rule' must be public.
    って怒られる
*/

    val rule: ActivityTestRule<MainActivity> = ActivityTestRule(MainActivity::class.java)

    @Rule
    public fun getActivityTestRule() = rule

    @Test
    public fun test() {
        val textView = rule.activity.findViewById(R.id.text) as TextView
        Assertions.assertThat(textView).isVisible()
        Assertions.assertThat(textView).hasText(R.string.app_name)
    }

}