BoxScreen.kt

@Composable
fun SimpleButtonDemo(){

    val textA = stringResource(id = R.string.textA)
    val textB = stringResource(id = R.string.textB)
    val colorA = colorResource(id = R.color.purple_200)
    val colorB = colorResource(id = R.color.teal_700)

    var text by remember{ mutableStateOf(textA)}
    var color by remember { mutableStateOf(colorA) }

    Box(
        modifier = Modifier.fillMaxSize().testTag("BOXTAG"),
        contentAlignment = Alignment.Center
    ){
        Button(
            onClick = {
                if(text == textA) {
                    text = textB
                    color = colorB
                } else{
                    text = textA
                    color = colorB
                }
            }
        ){
            Text(
                text = text,
                color = colorB,
                modifier = Modifier
                    .testTag("TEXTTAG")
            )
        }
    }
}

InstrumentedTextTextBoxScreen.kt

@RunWith(AndroidJUnit4::class)
class SimpleButtonInstTest {

    @get:Rule
    val rule = createComposeRule()

    @Before
    fun setup(){
        rule.setContent {
            SimpleButtonDemo()
        }
        rule.onNode(hasTestTag("BOXTAG"), useUnmergedTree = true).assertExists()
        rule.onNode(hasTestTag("TEXTTAG"), useUnmergedTree = true).assertExists()
    }

    @Test
    fun TestIfBoxExists(){
        rule.onNode(hasTestTag("BOXTAG"), useUnmergedTree = true)
            .assertExists()
    }

    @Test
    fun TextIfTextonButtonExists(){
        rule.onNode(hasTestTag("TEXTTAG"), useUnmergedTree = true)
            .assertExists()
    }
    
}