java - Dagger 2 generated test component not recognized

Question

I'm hoping that this is just something I'm doing wrong here. I'm trying to use Dagger 2.0 to inject dependencies for my JUnit tests (not Espresso tests, just pure JUnit). So, I have a 'main' java module and a 'test' java module. In the main module, I've got a Dagger Module and a Component:

@Module
public class MainModule {
    @Provides
    public Widget provideWidget() {
        return new ConcreteWidget();
    }
}

...

@Component (modules = MainModule.class)
public interface MainComponent {
    void inject(WidgetConsumer consumer);
}

And in my test module, I have the following:

@Module
public class TestModule {
    @Provides public Widget provideWidget() {
        return new Widget() {
            @Override
            public void doThing() {
                int y = 6;
                y ++;
            }
        };
    }
}

...

@Component(modules = TestModule.class)
public interface TestComponent extends MainComponent{
}

My build.gradle has dependencies that look like this:

dependencies {
    compile fileTree(dir: 'libs', include: ['*.jar'])
    androidTestCompile('com.android.support.test.espresso:espresso-core:2.2.2', {
        exclude group: 'com.android.support', module: 'support-annotations'
    })
    compile 'com.android.support:appcompat-v7:25.2.0'
    testCompile 'junit:junit:4.12'

    compile 'com.google.dagger:dagger:2.9'
    testCompile 'com.google.dagger:dagger:2.9'

    annotationProcessor 'com.google.dagger:dagger-compiler:2.9'
    testAnnotationProcessor 'com.google.dagger:dagger-compiler:2.9'
}

For whatever reason, Dagger generates DaggerMainComponent, but refuses to generate DaggerTestComponent. There appear to be no errors in the gradle output when I build.

Here's the thing... I think the annotation processor is running, but somehow the android gradle plugin is failing to pull in those generated sources during compile-time. I have inspected the app/build/generated/source/apt/test/ directory and found DaggerTestComponent.java in there, but for some reason, it's not imported as a dependency.

Any thoughts? Here is a link to a test project showing my issue

Answer 1

Add this to build.gradle after android DSL:

android {
    ...
}

android.applicationVariants.all {
    def aptOutputDir = new File(buildDir, "generated/source/apt/${it.unitTestVariant.dirName}")
    it.unitTestVariant.addJavaSourceFoldersToModel(aptOutputDir)
}

Thereafter, your test component would be recognized.

For Kotlin replace generated/source/apt/... with generated/source/kapt/...

There is an issue raised in the tracker concerning this.