LiveData extension property for use in unit tests

LiveData.kt

val <T> LiveData<T>.blockingValue: T?
    get() {
        var value: T? = null
        val latch = CountDownLatch(1)
        observeForever {
            value = it
            latch.countDown()
        }
        if (latch.await(2, TimeUnit.SECONDS)) return value
        else throw Exception("LiveData value was not set within 2 seconds")
    }