test-generator

A code generator for use with Anvil-KSP that simplifies dependency injection into junit4 test classes with a single @ContributesTest annotation.

For each class annotated with ContributesTest, a Dagger module will be generated with content similar to the following:

import ru.pixnews.anvil.ksp.codegen.test.inject.wiring.SingleInstrumentedTestInjector
import ru.pixnews.foundation.di.base.scopes.AppScope

@Module
@ContributesTo(AppScope::class)
object MyTest_TestModule {
  @Provides
  @IntoMap
  @ClassKey(MyTest::class)
  @SingleIn(AppScope::class)
  fun provideMyTestInjector(
      injector: MembersInjector<MyTest>
  ): SingleInstrumentedTestInjector = SingleInstrumentedTestInjector(injector)
}

This module is intended to add the specified class to the AppScope multibinding.

Code generator setup

Before using the generator, make sure Anvil-KSP is already configured in the project.

Then add the required dependencies:

dependencies {
    ksp("ru.pixnews.anvil.ksp.codegen:test-generator:0.1")

    // test-inject dependency is optional, all declarations this module can be overridden.
    implementation("ru.pixnews.anvil.ksp.codegen:test-inject:0.1")
}

The fully qualified names of annotation classes can be customized via KSP arguments in build.gradle.kts;

ksp {
    arg(
        "ru.pixnews.anvil.ksp.base.AppScope",
        "ru.pixnews.foundation.di.base.scopes.AppScope"
    )
    arg(
        "ru.pixnews.anvil.ksp.test.ContributesTest",
        "ru.pixnews.anvil.ksp.codegen.test.inject.ContributesTest"
    )
    arg(
        "ru.pixnews.anvil.ksp.test.SingleInstrumentedTestInjector",
        "ru.pixnews.anvil.ksp.codegen.test.inject.wiring.SingleInstrumentedTestInjector"
    )
}

By default, annotations from the test-inject module are used.

Project setup

To make use of this generator's output, the project must have test injection set up using Dagger multibindings. The configuration might look something like this (using classes from the test-inject module).

Add InstrumentedTestInjector to your application component:

import ru.pixnews.anvil.ksp.codegen.test.inject.wiring.InstrumentedTestInjector
import ru.pixnews.foundation.di.base.scopes.AppScope

@ContributesTo(AppScope::class)
interface InstrumentedTestInjectorHolder {
    val instrumentedTestInjector: InstrumentedTestInjector
}

Add multibinding to the application module:

import ru.pixnews.anvil.ksp.codegen.test.inject.wiring.DefaultInstrumentedTestInjector
import ru.pixnews.anvil.ksp.codegen.test.inject.wiring.InstrumentedTestInjector
import ru.pixnews.anvil.ksp.codegen.test.inject.wiring.SingleInstrumentedTestInjector
import ru.pixnews.foundation.di.base.DaggerMap
import ru.pixnews.foundation.di.base.scopes.AppScope

@ContributesTo(AppScope::class)
@Module
interface InstrumentedTestsInjectorsModule {
    @Multibinds
    fun instrumentedTestInjectors(): DaggerMap<Class<out Any>, SingleInstrumentedTestInjector>

    companion object {
        @Reusable
        @Provides
        fun provideInstrumentedTestInjector(
            injectors: DaggerMap<Class<out Any>, SingleInstrumentedTestInjector>,
        ): InstrumentedTestInjector {
            return DefaultInstrumentedTestInjector(injectors)
        }
    }
}

Create Junit4 TestRule with dependency injection:

class InjectDependenciesRule(
    private val instance: Any,
) : TestRule {
    override fun apply(base: Statement, description: Description): Statement {
        injectDependencies()
        return base
    }

    private fun injectDependencies() {
        (appComponent as InstrumentedTestInjectorHolder)
            .instrumentedTestInjector
            .inject(instance)
    }
}

Usage

Annotate your test with ContributesTest and use InjectDependenciesRule:

import ru.pixnews.anvil.ksp.codegen.test.inject.ContributesTest

@ContributesTest
class MyTest  {
    @get:Rule(order = 10)
    val injectDependencies = InjectDependenciesRule(this)

    @Inject
    lateinit var appConfig: AppConfig
}

The MyTest_TestModule module described above will be generated based on this annotation.

Packages

ru.pixnews.anvil.ksp.codegen.test.generator

jvm