Using Google Guice in Scala - http://michaelpnash.github.io/guice-up-your-scala/

testguice.scala

trait AService {
  def service: String
}

class SomeService extends AService {
  def service(): String = "someService"
}

class MyComponent @Inject()(val service: AService) {
  def callTheService(): String = service.service
}

class SomeOtherService extends AService {
  def service(): String = "someOtherService"
}

class DependencyInjectionTests extends FunSuite{

  test("Basic Test") {

    class ScalaModule extends AbstractModule {
      @Override
      protected def configure() {
        bind(classOf[AService]).to(classOf[SomeService])
      }
    }

    class ScalaModule2 extends AbstractModule {
      @Override
      protected def configure() {
        bind(classOf[AService]).to(classOf[SomeOtherService])
      }
    }

    val injector = Guice.createInjector(new ScalaModule)
    val component = injector.getInstance(classOf[MyComponent])
    assert("someService" === component.callTheService)

    val injector2 = Guice.createInjector(new ScalaModule2)
    val component2 = injector2.getInstance(classOf[MyComponent])
    assert("someOtherService" === component2.callTheService)

  }


  test("single instance of service") {

    // if you want to bind to a specific instance of a class...
    class InstanceExampleModule extends AbstractModule {
      @Override
      protected def configure() {
        val instance1 = new InstanceService("instance1")
        bind(classOf[AService]).toInstance(instance1)
      }
    }

    val injector = Guice.createInjector(new InstanceExampleModule)
    val service = injector.getInstance(classOf[AService])
    assert("instance1" === service.service)

  }

  class InstanceService(val value: String) extends AService {
    def service(): String = value
  }

}