Test Javascript method calling in WebView [Robolectric]

I'm trying to test whether Javascript method (registered as an interface in WebView) is called or not. Following sample works when executed within standard app flow, but it doesn't work when I try to run it like a Robolectric test. Anybody knows why?

@RunWith(RobolectricTestRunner::class)
@Config(sdk = [Build.VERSION_CODES.O_MR1])
class ExampleUnitTest {

    private lateinit var activityController: ActivityController<Activity>
    private lateinit var activity: Activity
    private lateinit var webView: WebView

    val signal = CountDownLatch(1)
    var success = false

    @Before
    fun setUp() {
        activityController = Robolectric.buildActivity(Activity::class.java)
        activity = activityController.get()
        webView = WebView(activity)
        webView.settings.javaScriptEnabled = true
        webView.addJavascriptInterface(this, "example")
    }

    @Test
    fun getUuid() {
        System.out.println("Ping")
        webView.evaluateJavascript("example.pong();", null);
        signal.await(10, TimeUnit.SECONDS)
        Assert.assertTrue(success)
    }

    @JavascriptInterface
    fun pong() {
        System.out.println("Pong")
        success = true
        signal.countDown()
    }
}