Espresso Snippet Example

This tutorial shows you how to create snippets that automate the UI of another app using Espresso.

The same approach can be used to create any snippet app that needs to access the classes or resources of any other single app.

Overview

To build a snippet that instruments another app, you have to create a new product flavor of your existing app with the snippet code built in.

The snippet code cannot run from a regular test apk because it requires a custom testInstrumentationRunner.

Tutorial

1. In the build.gradle file of your existing app, create a new product flavor called snippet.

   android {
     defaultConfig { ... }
     productFlavors {
       main {}
       snippet {}
     }
   }
   

2. Link against Mobly Snippet Lib in your build.gradle file

   dependencies {
     snippetCompile 'com.google.android.mobly:mobly-snippet-lib:1.3.1'
   }
   

3. Create a new source tree called src/snippet where you will place the snippet code.

4. In Android Studio, use the Build Variants tab in the left hand pane to switch to the snippetDebug build variant. This will let you edit code in the new tree.

5. Write your snippet code in a new class under src/snippet/java

   package com.my.app;
   ...
   public class EspressoSnippet implements Snippet {
     @Rpc(description="Pushes the main app button.")
     public void pushMainButton() {
       onView(withId(R.id.main_button)).perform(click());
     }
   
     @Override
     public void shutdown() {}
   }
   

6. Create src/snippet/AndroidManifest.xml containing an <instrument> block and any classes that implement the Snippet interface in meta-data

   <?xml version="1.0" encoding="utf-8"?>
   <manifest xmlns:android="http://schemas.android.com/apk/res/android">
     <application>
       <meta-data
         android:name="mobly-snippets"
         android:value="com.my.app.EspressoSnippet" />
     </application>
   
     <instrumentation
       android:name="com.google.android.mobly.snippet.SnippetRunner"
       android:targetPackage="com.my.app" />
   </manifest>
   

7. Build your apk by invoking the new assembleSnippetDebug target.

8. Install the apk on your phone. You do not need to install the main app's apk; the snippet-enabled apk is a complete replacement for your app.

9. In your Mobly python test, connect to your snippet .apk in setup_class

   class HelloWorldTest(base_test.BaseTestClass):
     def setup_class(self):
       self.ads = self.register_controller(android_device)
       self.dut1 = self.ads[0]
       self.dut1.load_snippet(name='snippet', package='com.my.app')
   

10. Invoke your needed functionality within your test

    def test_click_button(self):
      self.dut1.snippet.pushMainButton()
    

Running the example code

This folder contains a fully working example of a snippet apk that uses espresso to automate a simple app.

1. Compile the example

   ./gradlew examples:ex2_espresso:assembleSnippetDebug
   

2. Install the apk on your phone

   adb install -r ./examples/ex2_espresso/build/outputs/apk/snippet/debug/ex2_espresso-snippet-debug.apk
   

3. Use snippet_shell from mobly to trigger pushMainButton():

   snippet_shell.py com.google.android.mobly.snippet.example2
   
   >>> print(s.help())
   Known methods:
     pushMainButton(boolean) returns void  // Pushes the main app button, and checks the label if this is the first time.
     startMainActivity() returns void  // Opens the main activity of the app
   
   >>> s.startMainActivity()
   >>> s.pushMainButton(True)
   

4. Press ctrl+d to exit the shell and terminate the app.