Cannot resolve the Symbol Callback. Unable to import play.libs.F.Callback

I am implementing unit test using TestBrowser. I need to send the configuration to the test browser.

Here is the link of what I want to implement.

I write the code as :

@Test
public void testIndexPageRetrieval() {
    running(testServer(testPort, fakeApplication(configuration.asMap())), HTMLUNIT, new Callback<TestBrowser>() {
        @Override
        public void invoke(TestBrowser browser) {
          browser.maximizeWindow();
          IndexPage indexPage = new IndexPage(browser.getDriver(), testPort, 0);
          browser.goTo(indexPage);
          indexPage.isAt();
        } 
    });
}

Unable to import the Callback class. I tried import it manually but play.libs.F.Callback is not available. How do I can use Callback class or is there otherway around for this ?