[instrumentation_adapter] Update README instructions (flutter#2022)

(documentation-only change)

Author: collinjackson

packages/instrumentation_adapter/CHANGELOG.md

@@ -1,3 +1,7 @@
+## 0.0.2
+
+* Document current usage instructions, which require adding a Java test file.
+
 ## 0.0.1
 
 * Initial release

packages/instrumentation_adapter/README.md

@@ -22,6 +22,30 @@ void main() {
 }
 ```
 
+Create an instrumentation test file in your application's
+android/app/src/androidTest/java/com/example/myapp/ directory
+(replacing com, example, and myapp with values from your app's
+package name). You can name this test file MainActivityTest.java
+or another name of your choice.
+
+```
+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.runner.RunWith;
+
+@RunWith(FlutterRunner.class)
+public class MainActivityTest extends FlutterTest {
+  @Override
+  public void launchActivity() {
+    ActivityTestRule<MainActivity> rule = new ActivityTestRule<>(MainActivity.class);
+    rule.launchActivity(null);
+  }
+}```
+
 Use gradle commands to build an instrumentation test for Android.
 
 ```

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: 0.0.1
+version: 0.0.2
 author: Flutter Team <flutter-dev@googlegroups.com>
 homepage: https://github.com/flutter/plugins/tree/master/packages/instrumentation_adapter
 
@@ -16,4 +16,4 @@ dependencies:
 flutter:
   plugin:
     androidPackage: dev.flutter.plugins.instrumentationadapter
-    pluginClass: InstrumentationAdapterPlugin
+    pluginClass: InstrumentationAdapterPlugin