How to test DaggerFragment with FragmentScenario?

Question

I have a simple Fragment like so:

class SomeFragment : DaggerFragment() {
    ...
}

Now I want to test this Fragment using FragmentScenario

class LoginFragmentTest {

    @Test
    fun test() {
        launchFragmentInContainer<SomeFragment>()
        onView(withId(R.id.someButton))
            .check(matches(isDisplayed()))
    }

}

But everytime I try to the test its always:

java.lang.IllegalArgumentException: No injector was found for <...SomeFragment>

How can I properly run the test? Can anybody help me here?

Answer 1

I found two ways to solve the problem:

• using a separate build flavor for tests and typealias,
• creating your own DaggerFragment and special test variants of your fragments

I consider the first approach cleaner and would recommend to use it rather than the latter, but I'll describe both of them, so you can make your own choice.

---

Build flavors with typealias

1. Create two product flavors, mock and prod:

app/build.gradle

android {
    ...
    productFlavors {
        prod
        mock {
            applicationIdSuffix '.mock'
        }
    }
}

2. Then set the typealias depending on the flavor, let's call it BaseFragment:

prod flavor, app/src/prod/com.example.mypackage/BaseFragment.kt

typealias BaseFragment = DaggerFragment

mock flavor, app/src/mock/com.example.mypackage/BaseFragment.kt

typealias BaseFragment = Fragment

3. And finally use the BaseFragment alias in your fragments:

class SomeFragment : BaseFragment() {
   ...
}

4. To test the code using FragmentScenario switch from the prod* build variant to the mock* one and set all the dependencies that are supposed to be injected somewhere in your test class (e.g. using mocks)

---

Own DaggerFragment and test variants of the fragments

1. Create your own DaggerFragment (based on the actual dagger.android.support.DaggerFragment implementation):

abstract class DaggerFragment() : Fragment(), HasAndroidInjector {

    @Inject
    lateinit var androidInjector: DispatchingAndroidInjector<Object>

    override fun onAttach(context: Context) {
        injectMembers()
        super.onAttach(context)

    override fun androidInjector(): AndroidInjector<Object> = androidInjector

    protected open fun injectMembers() = AndroidSupportInjection.inject(this)
}

2. Extend your DaggerFragment implementation and set the fragment open:

open class SomeFragment : DaggerFragment() {
    ...
}

3. Create another implementation of your fragment for the test purposes and override the injectMembers method:

class TestSomeFragment : SomeFragment() {

    override injectMembers() {
        /* you can manually inject dependencies and mocks here */
    }
}

4. Use TestSomeFragment in your tests.