Dagger2 does not generate components in Test - robolectric

Question

As per the Dagger 2 documentation
I am trying to set up a test environment according to Dagger2's documentation
(Just for context, I have successfully done this in Dagger 1.)
The problem, specifically, is that while Dagger2 correctly generates DaggerRoboDaggerComponent (as used in App.java), it does not generate DaggerTestRoboDaggerComponent (as used in MainActivityTest.java). I have checked the directory structure to make sure it's not hiding in some obscure place, and done the requisite clean, rebuild, Invalidate Caches / Restart, etc.
If someone could please let me know the error of my ways, I'd appreciate it. Thanks in advance.
You can clone the project here
Or, browse thru the project files below:
build.gradle
apply plugin: 'com.android.application'
android {
compileSdkVersion 25
buildToolsVersion "25.0.2"
defaultConfig {
applicationId "xx.robodagger"
minSdkVersion 15
targetSdkVersion 25
versionCode 1
versionName "1.0"
testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
}
buildTypes {
release {
minifyEnabled false
proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
}
}
}
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-v7:25.3.1'
compile 'com.android.support.constraint:constraint-layout:1.0.2'
compile 'com.google.dagger:dagger:2.10'
annotationProcessor "com.google.dagger:dagger-compiler:2.10"
testCompile 'junit:junit:4.12'
testCompile "org.robolectric:robolectric:3.3.1"
}
App.java
package xx.robodagger;
import android.app.Application;
public class App extends Application {
static RoboDaggerComponent roboDaggerComponent;
static RoboDaggerComponent getComponent() {
return roboDaggerComponent;
}
#Override public void onCreate() {
super.onCreate();
roboDaggerComponent = DaggerRoboDaggerComponent.builder()
.roboDaggerModule(new RoboDaggerModule())
.build();
}
}
Foo.java
package xx.robodagger;
class Foo {
#Override public String toString() {
return "foo";
}
}
MainActivity.java
package xx.robodagger;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.widget.TextView;
import javax.inject.Inject;
public class MainActivity extends AppCompatActivity {
#Inject Foo foo;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
App.getComponent().inject(this);
setContentView(R.layout.activity_main);
TextView tv = (TextView)findViewById(R.id.textview);
tv.setText(foo.toString());
}
}
RoboDaggerComponent.java
package xx.robodagger;
import javax.inject.Singleton;
import dagger.Component;
#Singleton
#Component(modules={RoboDaggerModule.class})
interface RoboDaggerComponent {
void inject(MainActivity mainActivity);
}
RoboDaggerModule.java
package xx.robodagger;
import javax.inject.Singleton;
import dagger.Module;
import dagger.Provides;
#SuppressWarnings("unused")
#Module
class RoboDaggerModule {
#Provides
#Singleton
Foo providesFoo() { return new Foo(); }
}
And now in the test directory,
FakeFoo.java
package xx.robodagger;
class FakeFoo extends Foo {
#Override public String toString() {
return "bar";
}
}
MainActivityTest.java
import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.robolectric.RobolectricTestRunner;
import org.robolectric.annotation.Config;
import javax.inject.Inject;
#RunWith(RobolectricTestRunner.class)
#Config(constants = BuildConfig.class)
public class MainActivityTest {
TestRoboDaggerComponent testRoboDaggerComponent;
#Inject Foo foo;
#Before
public void setup() {
testRoboDaggerComponent = DaggerTestRoboDaggerComponent.builder()
.testRoboDaggerModule(new TestRoboDaggerModule())
.build();
testRoboDaggerComponent.inject(this);
}
#Test
public void fooBarTest() {
assert(foo.toString().equals("bar"));
}
}
TestRoboDaggerComponent.java
package xx.robodagger;
import javax.inject.Singleton;
import dagger.Component;
#Singleton
#Component(modules={TestRoboDaggerModule.class})
interface TestRoboDaggerComponent {
void inject(MainActivityTest mainActivityTest);
}
TestRoboDaggerModule.java
package xx.robodagger;
import javax.inject.Singleton;
import dagger.Module;
import dagger.Provides;
#SuppressWarnings("unused")
#Module
class TestRoboDaggerModule {
#Provides
#Singleton
Foo providesFoo() { return new FakeFoo(); }
}

Answer 1

Delete TestRoboDaggerComponent.java, it's not needed
Modify App.java to setup the component via a protected method
#Override public void onCreate() {
super.onCreate();
setupComponent();
}
protected void setupComponent() {
roboDaggerComponent = DaggerRoboDaggerComponent.builder()
.roboDaggerModule(new RoboDaggerModule())
.build();
}
Modify TestApp.java to extend App, and override the previously mentioned method with the TestModule
public class TestApp extends App {
#Override
protected void setupComponent() {
roboDaggerComponent = DaggerRoboDaggerComponent.builder()
.roboDaggerModule(new TestRoboDaggerModule())
.build();
}
}
And finally, in the actual test, leverage Robolectric's power to specify the Application module
#RunWith(RobolectricTestRunner.class)
#Config(constants = BuildConfig.class,
application = TestApp.class)
public class MainActivityTest {
private MainActivity mainActivity;
#Before
public void setup() {
mainActivity = Robolectric.setupActivity(MainActivity.class);
}
#Test
public void fooBarTest() {
TextView tv = (TextView)mainActivity.findViewById(R.id.textview);
assert(tv.getText().equals("bar"));
}
}
Notice that there isn't any DI in the actual test proper. The injection of MainActivity takes place as expected, and with the overridden module. If you have a dependency that uses #Injects in the constructor, the solution per Dagger's documentation is not to use injection in the test, but to just call the normal constructor with mocked objects. This all makes sense. I still think the originally reported issue is a bug, but whatever.