How to create mock VaadinSession for integration tests?

My Issue:

This is my first time doing tests for Vaadin UI and I am also fairly new to Unit tests in general. My issue is that I can't do anything with my UI components Views because there is no VaadinSession which handles the UI beans. A VaadinSession is never created when using @SpringBootTest. I was able to create tests for my backend since Spring handles those beans, but I can't seem to figure out a way to get Vaadin to start up a session so I can then access the session and do different integration and unit tests.

What I've Tried

TestBench: The Vaadin testbench seemed like a very good option but the issue that I faced was that it doesn't seem to open a VaadinSession whenever I open a ChromeDriver() that goes to the website on my localhost.

Karibu Library: This library seemed like a very good option, but there was one issue, which was that it opens individual UI components that are instantiated, however a couple of my UI Components Classes, uses dependency injection to inject backend services. I cannot instantiate these classes because of the dependeny injection.

The UI Component that I need to access through the VaadinSession.

@Component
@UIScope
@CssImport("./styles/current-info-styles.css")
public class CurrentDayView extends VerticalLayout implements Updatable {
    private static final long serialVersionUID = 1L;

    //Some code here

    @Autowired
    public CurrentDayView(NowcastWeatherService nowcastWeatherService, GeoLocationService geoLocationService) {
        this.nowcastWeatherService = nowcastWeatherService;
        this.geoLocationService = geoLocationService;

        //Some Code here
    }
   //Some code here

My Testbench approach

@RunWith(SpringRunner.class)
@SpringBootTest
public class CurrentDayViewTest extends TestBenchTestCase {

    @Test
    public void fakeTest() {
        Assert.assertTrue(true);
    }

    @Before
    public void startUp() {
        System.setProperty("webdriver.chrome.driver", "src/main/resources/drivers/chromedriver.exe");
        setDriver(new ChromeDriver());
        getDriver().get("http://localhost:8080/");

        populateViewWithInformation();
    }

    @After
    public void tearDown() {
        getDriver().quit();
    }

    private void populateViewWithInformation() {
        CurrentDayView currentDayView = (CurrentDayView) VaadinSession.getCurrent().getAttribute("current-day-view");
        //This is where I get an error because VaadinSession.getCurrent() is null
    }

My Final Question:

Does anyone have any idea on how I could have a VaadinSession created or atleast get spring to keep track for Vaadin UI components? If this wasn't clear then please feel free to ask more clarifications relating to my question.

I suggest you give Karibu another shot, it's great for doing these kinds of tests that don't need the app to be running.

Take a look at the Karibu V14 Spring demo project. Pay attention to what Karibu dependency is used. The ApplicationTest#listOrders test contains navigation to a view with autowired dependencies.

The issue with your TestBench test is that TestBench is used to test against a running application, and the tests run in an entirely different process than the actual application.

So when you open the page with the driver, a Vaadin session is created in the application, but you will not be able to access it in your tests, nor will you be able to access any UI state or views. What it allows you to do, however, is to interact with the application as you would do through the browser (clicking buttons, filling in text fields etc.), and to check that the state in the browser is correct, without knowing anything about the server's internal state.

Generally speaking, when you're writing integration tests with TestBench (which is based on Selenium), what you're doing is directing the browser. You're writing Java code, yes, and the code may even be in the same project as your Vaadin UI code, but it can be executed against any URL and what you're interacting with is the browser's DOM. You're describing what the end-user would do: click a button, write some text in an input field, choose an option from a radio button group. The server-side is a black box. After all, if I submit a post on StackOverflow, I can't check if it gets stored in a database - all I can do is look at what I see after I press the "Post your answer" button. If you really want to nitpick, it doesn't even need to be a Vaadin application you're testing with TestBench, as long as the application behaves like one in the browser.

Secondly, you shouldn't store any Components in the VaadinSession. If you open a Vaadin application in multiple browser tabs, each of those tabs will share the same VaadinSession. A single Component instance should only be used inside one browser tab, where the root component is the current UI.