How to combine different testInstrumentationRunner

Is there any way to have different testInstrumentationRunner for each test? Do I have to create a Task for it? I have my runner as follows :

class MyTestRunner : AndroidJUnitRunner() {
    override fun newApplication(
        cl: ClassLoader?,
        className: String?,
        context: Context?
    ): Application {
        return super.newApplication(cl, MyTestApp::class.java.name, context)
    }
}

But what if I want to run some using the real app? how can I choose it?

I've been reading that is possible doing it with @RunWith(AndroidJUnit4ClassRunner::class)on my tests I'm using it but I understand if I do this it takes the one of the defaultConfig

defaultConfig {
        testInstrumentationRunner("mypackage.MyTestRunner")
}

But I can not use something like

@RunWith(MyTestRunner::class)

In case I could do this I'd understand how can I use different runners.