From d7ad50bcf7bdf2e519729a583a568d858e9e185f Mon Sep 17 00:00:00 2001
From: Collin Jackson <jackson@google.com>
Date: Tue, 27 Aug 2019 17:17:32 -0700
Subject: [PATCH] [instrumentation_adapter] update boilerplate to use @Rule
 instead of FlutterTest (#2023)

* Updates the boilerplate test to use `@Rule` instead of `FlutterTest`, bringing it more in line with how native Android tests work.
---
 packages/instrumentation_adapter/CHANGELOG.md |  4 +++
 packages/instrumentation_adapter/README.md    | 15 +++++------
 .../instrumentationadapter/FlutterRunner.java | 25 +++++++++++++++----
 .../instrumentationadapter/FlutterTest.java   |  9 -------
 packages/instrumentation_adapter/pubspec.yaml |  2 +-
 5 files changed, 31 insertions(+), 24 deletions(-)
 delete mode 100644 packages/instrumentation_adapter/android/src/main/java/dev/flutter/instrumentationadapter/FlutterTest.java

diff --git a/packages/instrumentation_adapter/CHANGELOG.md b/packages/instrumentation_adapter/CHANGELOG.md
index d5326e512537..ace51df0cc1c 100644
--- a/packages/instrumentation_adapter/CHANGELOG.md
+++ b/packages/instrumentation_adapter/CHANGELOG.md
@@ -1,3 +1,7 @@
+## 0.1.0
+
+* Update boilerplate test to use `@Rule` instead of `FlutterTest`.
+
 ## 0.0.2
 
 * Document current usage instructions, which require adding a Java test file.
diff --git a/packages/instrumentation_adapter/README.md b/packages/instrumentation_adapter/README.md
index 972790bae5e0..49a33954cfbe 100644
--- a/packages/instrumentation_adapter/README.md
+++ b/packages/instrumentation_adapter/README.md
@@ -33,18 +33,15 @@ package com.example.myapp;
 
 import androidx.test.rule.ActivityTestRule;
 import dev.flutter.plugins.instrumentationadapter.FlutterRunner;
-import dev.flutter.plugins.instrumentationadapter.FlutterTest;
-import java.lang.Override;
+import org.junit.Rule;
 import org.junit.runner.RunWith;
 
 @RunWith(FlutterRunner.class)
-public class MainActivityTest extends FlutterTest {
-  @Override
-  public void launchActivity() {
-    ActivityTestRule<MainActivity> rule = new ActivityTestRule<>(MainActivity.class);
-    rule.launchActivity(null);
-  }
-}```
+public class MainActivityTest {
+  @Rule
+  public ActivityTestRule<MainActivity> rule = new ActivityTestRule<>(MainActivity.class);
+}
+```
 
 Use gradle commands to build an instrumentation test for Android.
 
diff --git a/packages/instrumentation_adapter/android/src/main/java/dev/flutter/instrumentationadapter/FlutterRunner.java b/packages/instrumentation_adapter/android/src/main/java/dev/flutter/instrumentationadapter/FlutterRunner.java
index bc635ea080de..c823306e022c 100644
--- a/packages/instrumentation_adapter/android/src/main/java/dev/flutter/instrumentationadapter/FlutterRunner.java
+++ b/packages/instrumentation_adapter/android/src/main/java/dev/flutter/instrumentationadapter/FlutterRunner.java
@@ -4,8 +4,12 @@
 
 package dev.flutter.plugins.instrumentationadapter;
 
+import android.app.Activity;
+import androidx.test.rule.ActivityTestRule;
+import java.lang.reflect.Field;
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
+import org.junit.Rule;
 import org.junit.runner.Description;
 import org.junit.runner.Runner;
 import org.junit.runner.notification.Failure;
@@ -15,13 +19,24 @@ public class FlutterRunner extends Runner {
 
   final Class testClass;
 
-  public FlutterRunner(Class<FlutterTest> testClass) {
+  public FlutterRunner(Class<?> testClass) {
     super();
     this.testClass = testClass;
-    try {
-      testClass.newInstance().launchActivity();
-    } catch (InstantiationException | IllegalAccessException e) {
-      throw new IllegalThreadStateException("Unable to launch test");
+
+    // Look for an `ActivityTestRule` annotated `@Rule` and invoke `launchActivity()`
+    Field[] fields = testClass.getDeclaredFields();
+    for (Field field : fields) {
+      if (field.isAnnotationPresent(Rule.class)) {
+        try {
+          Object instance = testClass.newInstance();
+          ActivityTestRule<Activity> rule = (ActivityTestRule<Activity>) field.get(instance);
+          rule.launchActivity(null);
+        } catch (InstantiationException | IllegalAccessException e) {
+          // This might occur if the developer did not make the rule public.
+          // We could call field.setAccessible(true) but it seems better to throw.
+          throw new RuntimeException("Unable to access activity rule", e);
+        }
+      }
     }
   }
 
diff --git a/packages/instrumentation_adapter/android/src/main/java/dev/flutter/instrumentationadapter/FlutterTest.java b/packages/instrumentation_adapter/android/src/main/java/dev/flutter/instrumentationadapter/FlutterTest.java
deleted file mode 100644
index df6b398bddd6..000000000000
--- a/packages/instrumentation_adapter/android/src/main/java/dev/flutter/instrumentationadapter/FlutterTest.java
+++ /dev/null
@@ -1,9 +0,0 @@
-// Copyright 2019 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-package dev.flutter.plugins.instrumentationadapter;
-
-public abstract class FlutterTest {
-  public abstract void launchActivity();
-}
diff --git a/packages/instrumentation_adapter/pubspec.yaml b/packages/instrumentation_adapter/pubspec.yaml
index 693ad090f5e1..0d67157ba80f 100644
--- a/packages/instrumentation_adapter/pubspec.yaml
+++ b/packages/instrumentation_adapter/pubspec.yaml
@@ -1,6 +1,6 @@
 name: instrumentation_adapter
 description: Runs tests that use the flutter_test API as platform native instrumentation tests.
-version: 0.0.2
+version: 0.1.0
 author: Flutter Team <flutter-dev@googlegroups.com>
 homepage: https://github.com/flutter/plugins/tree/master/packages/instrumentation_adapter