android-testing-guide

Android Testing Guide

Show some :heart:

Complete reference for Android Testing with examples.

Contents

• Introduction
  • Why testing?
  • Why unit test?
  • Instrumented tests
• Local Tests
  • JUnit basics
  • Beyond JUnit basics
  • Assertions
  • Hamcrest
  • Assertj
  • Rules
  • Mockito
  • PowerMock
  • EasyMock
  • WireMock
  • RESTMock
• Android
  • Android test rules
    • Rule to test Android Activity
    • Rule to test Android Service
    • Rule to test Android Intents
  • Android instrumented tests
  • Test filtering
  • Espresso
    • Basics
    • Testing RecyclerView
    • Testing Toast
    • Testing Intents
    • Testing Synchronization with background jobs
  • Robolectric
    • Testing Activities
    • Testing Fragments
    • Testing sqlite
  • Robotium
  • UI testing and UI Automator
  • MonkeyRunner
• References

Introduction

Why testing?

• Testing forces you to think in a different way and implicitly makes your code cleaner in the process.
• You feel more confident about your code if it has tests.
• Shiny green status bars and cool reports detailing how much of your code is covered are both consequences of writing tests.
• Regression testing is made a lot easier, as automated tests would pick up the bugs first.

Why unit test?

A unit test generally exercises the functionality of the smallest possible unit of code (which could be a method, class, or component) in a repeatable way.

Tools that are used to do this testing:

• JUnit – normal test assertions.
• Mockito – mocking out other classes that are not under test.
• PowerMock – mocking out static classes such as Android Environment class etc.

Instrumented tests

A UI Test or Instrumentation Test mocks typical user interactions with your app. Clicking on buttons, typing in text are some of the things UI Tests can complete.

• Espresso – Used for testing within your app, selecting items, making sure something is visible.
• UIAutomator – Used for testing interaction between different apps.

There are other tools that are available for this kind of testing such as Robotium, Appium, Calabash, Robolectric.

Local Tests

JUnit basics

Calculator.java

public class Calculator {

    public int add(int op1, int op2) {
        return op1 + op2;
    }

    public int diff(int op1, int op2) {
        return op1 - op2;
    }

    public double div(int op1, int op2) {
        // if (op2 == 0) return 0;
        return op1 / op2;
    }
}

CalculatorTest.java

…

Beyond JUnit basics

CalculatorTest.java

@Ignore
@Test(expected = java.lang.ArithmeticException.class)
public void testDivWithZeroDivisor() {
    calculator = new Calculator();
    double total = calculator.div(9, 0);
    assertEquals("Calculator is not handling division by zero correctly", 0.0, total, 0.0);
}

Assertions

JUnit provides overloaded assertion methods for all primitive types and Objects and arrays (of primitives or Objects). The parameter order is expected value followed by actual value. Optionally the first parameter can be a String message that is output on failure. There is a slightly different assertion, assertThat that has parameters of the optional failure message, the actual value, and a Matcher object. Note that expected and actual are reversed compared to the other assert methods.

AssertTests.java

…

Hamcrest

HamcrestTest.java

…

Rules

CalculatorWithTestName.java

public class CalculatorWithTestName {

    @Rule
    public TestName name = new TestName();

    @Test
    public void testAdd() {
        Calculator calculator = new Calculator();
        int total = calculator.add(4, 5);
        assertEquals(name.getMethodName() + " adding incorrectly", 9, total);
    }

    @Test
    public void testDiff() {
        Calculator calculator = new Calculator();
        int total = calculator.diff(12, 7);
        assertEquals(name.getMethodName() + " subtracting incorrectly", 5, total);
    }
}

RESTMock

RESTMock is a library working on top of Square's okhttp/MockWebServer. It allows you to specify Hamcrest matchers to match HTTP requests and specify what response to return. It is as easy as:

RESTMockServer.whenGET(pathContains("users/defunkt"))
            .thenReturnFile(200, "users/defunkt.json");

Step 1: Start the server

It's good to start server before the tested application starts, there are few methods:

a) RESTMockTestRunner

To make it simple you can just use the predefined RESTMockTestRunner in your UI tests. It extends AndroidJUnitRunner:

defaultConfig {
        ...
        testInstrumentationRunner 'io.appflate.restmock.android.RESTMockTestRunner'
    }

b) RESTMockServerStarter

If you have your custom test runner and you can't extend RESTMockTestRunner, you can always just call the RESTMockServerStarter. Actually RESTMockTestRunner is doing exactly the same thing:

public class MyAppTestRunner extends AndroidJUnitRunner {
    ...
    @Override
    public void onCreate(Bundle arguments) {
        super.onCreate(arguments);
        RESTMockServerStarter.startSync(new AndroidAssetsFileParser(getContext()),new AndroidLogger());
        ...
    }
    ...
}

Step 2: Specify Mocks

a) Files

By default, the RESTMockTestRunner uses AndroidAssetsFileParser as a mocks file parser, which reads the files from the assets folder. To make them visible for the RESTMock you have to put them in the correct folder in your project, for example:

.../src/androidTest/assets/users/defunkt.json

This can be accessed like this:

RESTMockServer.whenGET(pathContains("users/defunkt"))
            .thenReturnFile(200, "users/defunkt.json");

b) Strings

If the response You wish to return is simple, you can just specify a string:

RESTMockServer.whenGET(pathContains("users/defunkt"))
            .thenReturnString(200, "{}");

c) MockResponse

If you wish to have a greater control over the response, you can pass the MockResponse

RESTMockServer.whenGET(pathContains("users/defunkt")).thenReturn(new MockResponse().setBody("").setResponseCode(401).addHeader("Header","Value"));

Step 3: Request Matchers

You can either use some of the predefined matchers from RequestMatchers util class, or create your own. remember to extend from RequestMatcher

Step 4: Specify API Endpoint

The most important step, in order for your app to communicate with the testServer, you have to specify it as an endpoint for all your API calls. For that, you can use the RESTMockServer.getUrl(). If you use Retrofit, it is as easy as:

RestAdapter adapter = new RestAdapter.Builder()
                .baseUrl(RESTMockServer.getUrl())
                ...
                .build();

Request verification

It is possible to verify which requests were called and how many times thanks to RequestsVerifier. All you have to do is call one of these:

//cheks if the GET request was invoked exactly 2 times
RequestsVerifier.verifyGET(pathEndsWith("users")).exactly(2);

//cheks if the GET request was invoked at least 3 times
RequestsVerifier.verifyGET(pathEndsWith("users")).atLeast(3);

//cheks if the GET request was invoked exactly 1 time
RequestsVerifier.verifyGET(pathEndsWith("users")).invoked();

//cheks if the GET request was never invoked
RequestsVerifier.verifyGET(pathEndsWith("users")).never();

Logging

RESTMock supports logging events. You just have to provide the RESTMock with the implementation of RESTMockLogger. For Android there is an AndroidLogger implemented already. All you have to do is use the RESTMockTestRunner or call

RESTMockServerStarter.startSync(new AndroidAssetsFileParser(getContext()),new AndroidLogger());

or

RESTMockServer.enableLogging(RESTMockLogger)
RESTMockServer.disableLogging()

Android

Android test rules

Rule to test Android Activity

MainActivityTestRule.java

…

Rule to test Android Service

SampleServiceTestRule.java

…

Android instrumented tests

Testing Android Activity

MainActivityTest.java

…

Testing Android Service

SampleServiceTest

…

Test filtering

MainActivityTest.java

…

Espresso

MainActivityTest.java

…

Robolectric

MainActivityRoboelectricTest.java

@RunWith(RobolectricGradleTestRunner.class)
@Config(constants = BuildConfig.class)
public class MainActivityRoboelectricTest {

    private Mai