Starting the activity with composable

Code

class MainActivity : ComponentActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContent {
            ComposetestingTheme {
                // A surface container using the 'background' color from the theme
                Surface(
                    modifier = Modifier.fillMaxSize(),
                    color = MaterialTheme.colorScheme.background
                ) {
                    DisplayButtonDemo()
                }
            }
        }
    }
}

Test

class MainActivityTest {

    @get:Rule
    val composeTestRule = createAndroidComposeRule<MainActivity>()

    @Test
    fun myTest() {
        composeTestRule.onNodeWithText("Hello World!").performClick()
    }

}