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Saturday, April 27, 2013

Testing Android Apps with Junit (no more slow emulator)

Hi there, today i wanna share a very helpful way to test our Android Apps with fast Junit tests instead of using the "slow emulator". With Junit you'll speed up your development and ensure quality.

  • Your Project must use at a minimum platform 2.2 Google API level 8. (This is the most cases)
  • You must use Junit 4 Library and not Junit 3.
  • Download the newst jar file from here: robolectric-X.X.X-all.jar 
How to do it? 
  1. Create your Android project normally.
  2. select your project and add a new folder called test like the pic bellow.

Creating a Junit Test Project
Create a simple Java-Project (attention not another Android-Project) with the same name as your Android project but with the suffix -Test at the end and click next. (Attenion: do not press finish)  
Ex: MyProject and MyProjectTest

Select the src-folder, right mouse click and select "remove source folder" from build path. (the src folder will change from source into normal folder. see picture bellow after point 4)

Select the src-folder, right mouse click and take "Link additional source" and browse the created test folder from your Android Project and then click finish. The result will be something like point 1 in the pic above.

Create a folder called lib in your test project like point 4 in the picture above and copy/paste the downloaded roboelectric-x.x.x-all.jar into it.

Now select your test project, right mouse click, select Build Path > Configure Build Path... > select tab libraries > add library > Junit > next > select Junit 4 > click finish but stay in this dialog.

Click add jars... > select your test project (in this example here: MyProjectTest) > lib > select roboelectric-x.x.x-jar > click ok but stay in this dialog. (see picture bellow point 1)

Click add external jars... > [browse the location from your android-sdk] > platforms > android 8 > select android.jar > click ok but stay in this dialog. (see picture bellow point 1)

Click add external jars... > [browse the location from your android-sdk] > add-ons> addons-google_apis-android-8 > libs > select maps.jar > click ok. (see picture bellow point 1)

Select the Tab Projects > add your test project to it like the picture bellow. After that press the refresh key (F5) and run a project clean. (Project > clean...) (see picture bellow)

Setup your test run configuration
Attention: This step is very important. It will not work, if you don't do it.

Select menu run > run configurations... > double click Junit > and follow the steps in the picture bellow:

Write your first test to validate all those steps
Go back to your test project (in this case here MyProjectTest) and create a simple class in the test folder called MyActivityTest and copy the next code lines into it.

package com.example;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.junit.Assert.assertThat;

import org.junit.Test;
import org.junit.runner.RunWith;

import com.example.myproject.MainActivity;
import com.example.myproject.R;
import com.xtremelabs.robolectric.RobolectricTestRunner;

public class MyActivityTest {

    public void shouldHaveHappySmiles() throws Exception {
        String hello = new MainActivity().getResources().getString(R.string.hello_world);
        assertThat(hello, equalTo("Hello world!"));

Run the test
Menu > Run > Run Configurations... > select Junit > select your created MyProjectTestConfiguration and run it. If everything went well, we should get something like this:

So bye bye slow emulator... ;-) happy coding!