Overview

When we write unit tests for an Android application, sometimes there’s a necessity to mock some classes or interfaces. Instead of writing implementations dedicated for unit tests by hand, we can use Mockito library. We can read article about Mockito on Android on Square’s blog. Mockito can make our tests cleaner and better. It can be used both in classic Java projects and Android projects. It’s one of the most popular mocking framework in Java and if you’re a Java developer who writes unit tests and tries to apply TDD approach, you should be familiar with it.

Sample configuration

When we want to use Mockito on Android, we have to remember to add dependency to dexmaker 1.0 and dexmaker-mockito 1.0.

Sample test configuration in build.gradle file can look as follows (I’ve added more comments to clarify optional doubts):

dependencies {
    // our project dependencies go here...

    androidTestCompile 'com.android.support.test:testing-support-lib:0.1' // Android testing support library
    androidTestCompile('com.google.truth:truth:0.25') { // Google's library for assertions (not required by Mockito)
        exclude group: 'junit' // Android has JUnit built in
    }
    androidTestCompile 'com.google.dexmaker:dexmaker:1.0' // required by Mockito
    androidTestCompile 'com.google.dexmaker:dexmaker-mockito:1.0' // required by Mockito
    androidTestCompile 'org.mockito:mockito-core:1.9.5'
}

We should also add information about tesInstrumentationRunner to build.gradle file when we are using it.
When we have problems with running our tests, we should configure packagingOptions properly.

android {
    defaultConfig {
        ...
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
    }
    packagingOptions {
        exclude 'LICENSE.txt'
        exclude 'META-INF/LICENSE.txt'
    }
}

Remember

Quotation from Mockito website:

  • Do not mock types you don’t own
  • Don’t mock value objects
  • Don’t mock everything
  • Show love with your tests!

References