How do I use multiple custom test runners in Android?

Question

I am overriding Dagger 2 Components to mock dependencies in Android. For this I am using custom JUnit TestRunners.

It seems in my app/build.gradle I can set only one testRunner.

defaultConfig {
    applicationId 'com.xxx.xxx'
    minSdkVersion 18
    targetSdkVersion 23
    versionCode 1
    versionName '1.0.0'

    testInstrumentationRunner 'com.xxx.xxx.DgMockTestRunner'
}

How can I set multiple test runners? I would like every test class I write to have a separate TestRunner?

Answer 1

You can use the @RunWith annotation in your test classes to specify the test runner class:

@RunWith(FooTestRunner.class)
public class TestFoo {
    @Before
    public void setUp();
}

However, in general you can probably accomplish what you want to do using JUnit rules. For example, the following DaggerMock rule instantiates a new MyComponent with a MyModule and sets this as the root component in the application:

@Rule public DaggerMockRule<MyComponent> daggerRule = new DaggerMockRule<>(MyComponent.class, new MyModule())
        .set(new DaggerMockRule.ComponentSetter<MyComponent>() {
            @Override public void setComponent(MyComponent component) {
                App app = (App) InstrumentationRegistry.getInstrumentation().getTargetContext().getApplicationContext();
                app.setComponent(component);
            }
        });