testing LiveData

ExampleTest.kt

 ExampleTest{    
     @BeforeEach
     fun setUp() {
        viewModel = SomeViewModel(...)

        filtersObserver = viewModel.filtersLiveData.observeEvents()
    }
   
    @Test fun `test 1`(){
      val expected = arrayListOf<Any>()
      viewModel.requestSomeArrayList(Any())

        assertEquals(filtersObserver.firstValue(), expected)
    }
   
    @AfterEach
    fun tearDown() {
        viewModel.filtersLiveData.removeObserver(filtersObserver)
    }
 }

LiveData.kt

import androidx.lifecycle.LiveData

internal fun <T> LiveData<T>.observeEvents() = TestObserver<T>().also { observeForever(it) }

TestObserver.kt

import androidx.lifecycle.Observer

internal class TestObserver<T> : Observer<T> {

    val observedValues = mutableListOf<T?>()

    override fun onChanged(value: T?) {
        observedValues.add(value)
    }

    fun firstValue() = observedValues.first()
}