How can I unit test Android View animation endAction?

fun TextView.setTextWithFade(text: String, duration: Long = 300) {
    this.animate().alpha(0f).setDuration(duration).withEndAction {
        this.text = text
        this.animate().alpha(1f).setDuration(duration).start()
    }.start()
}

Hello, I have a simple Kotlin extension function for a TextView to change text with animation. There is three steps in this animation:

1. Fades out old text
2. Change the text in a TextView
3. Fades the text back in

What is the best way to write Unit Test that checks, whether the text was changed after the fade out animation?

@Test
fun setTextWithFadeTest() {
    val context = ApplicationProvider.getApplicationContext<Context>()
    val textView = TextView(context)
    textView.text = "test1"
    textView.setTextWithFade("test2", duration = 10)

    val handler = Handler()
    handler.postDelayed({
        println("Text: ${textView.text}, alpha: ${textView.alpha}")
        assert(textView.text == "test2")
    }, 300)

    Robolectric.getForegroundThreadScheduler().advanceBy(300, TimeUnit.MILLISECONDS)
}

This is a code how I try to achieve it. That handler prints:

Text: test1, alpha: 1.0

So it seems that animation don't even started.