SafeTest: A novel approach to front end testing

[willio58]

Lots of negativity in the comments but I think the solutions outlined really interesting and valuable! There are some idiosyncrasies around unit testing ui that are just hard to work around. And the issues with e2e tests in the context of testing individual UI pieces are totally valid too.

The one thing that at least initially rubs me the wrong way is how the overrides work. Like I get why that's a solution to how we can inject some data, but I don't like the idea of writing test-specific code in a component just to enable tests with this tool. That being said, I've done similar things in the past when I've run out of options and this looks pretty clean, I just wonder if there's another way.

[drewcoo]

> Conversely, using integration testing tools like Cypress or Playwright provides control over the page, but sacrifices the ability to instrument the bootstrapping code for the app. These tools operate by remotely controlling a browser to visit a URL and interact with the page.

I don't think the author has used Cypress or Playwright. Their real value is that they do not drive browsers from the outside like slow, flakey WebDriver. They also allow injecting test doubles. And to override app functionality (not having to wait for a "normal" 60 second timeout like the author hypothetically suggests).

This test framework seems to solve non-problems.

Is Netflix not quite so FAANG these days?

[kolodny]

Author here. Can you show an example of how Playwright would progress a timer on a page? For example, how would you make this component pass faster than 60 seconds?

    export const Countdown = () => {
      const [time, setTime] = React.useState(60);
      React.useEffect(() => {
        const interval = setInterval(() => {
          setTime(t => t - 1);
          if (t === 1) clearInterval(interval);
        }, 1000);

        return () => clearInterval(interval)
      }, []);

      return time > 0 ? <>Time left {time}</> : <>Done</>
    };

Short of using Playwright Component Tests, this isn't possible.

I also found an issue where the only solution was to inject sinon into the page which I wouldn't consider a great option: https://github.com/microsoft/playwright/issues/10230

[zie]

I've always wanted to build a UX tester that uses accessibility tech. We get to test both at the same time, and it might make the accessibility tech saner and easier to use also.

[thom]

I think this is overselling itself a little. It seems genuinely useful to be able to do more expansive integration tests of components, and combinations of components, especially running in real browsers. But that’s only really an incremental gain over component unit tests with mocks. In the case where you own a very complex SPA with multiple back end dependencies you don’t control, then yeah, maybe this is all you need. But I don’t see how this can replace real end to end functional tests in most apps.

[s4i]

Needing to change the application code to mock things rubs me the wrong way. I 100% do agree with the frontend testing challenges they lay out in the beginning of the post though.

[5Qn8mNbc2FNCiVV]

No different than any other dependency injection

[foolswisdom]

My initial impression of this is that it enables controlling just how much of the app you want to render for your test, while more traditional solutions force you towards either rendering the whole app or testing just a component. Is that accurate?

[kolodny]

Yes, that's correct. You get all the benefits of react-testing-library mounting and the ability to test the entire app as a unit.

[somewhereoutth]

I've said it before, and I'll say it again: Interfaces used by humans must be tested by humans. These can either be your staff, or your customers.

Yes that does mean wading through each interaction pathway every time you make a release, there really is no substitute.

[technion]

I think netflix is at a scale where you can question what I'm saying below, but every frontend test suit I've seen is so full of mocks you basically only test your own test suite. And then common front end bugs like "renders off the screen" or "doesnt work in safari" aren't caught anyway.

I hugely support tests and I write a lot more of them than most people. I just don't think it usually works on the frontend.

[bryanrasmussen]

Are there potential performance issues to consider with overrides - I'm supposing

const FetchPerson = createOverride(fetchPerson);

must be less performant by some amount than just using fetchPerson? How many over-rides do you find a reasonably complex component needs?

[kolodny]

React is pretty performant when context isn't changing. We haven't done any benchmarking but I doubt there's any real world perf hit. For large applications the number of overrides tend to be under 20.

Overrides are opt-in so you can just expose any overridable value as a prop and run a isolated component test on it.

[greatjack613]

Not sure why this is fundamentally different from existing e2e testers with bootstrapping

[kolodny]

Can you clarify what you mean? Usually, e2e testers don't have a bootstrapping stage for app-level changes, only for things that can be done via the browser automation APIs.

[mdaniel]

how many billions of dollars and they still host their blog on a nagware site SMH It's not like moving would be high drama since they already have a custom domain for it

https://scribe.rip/introducing-safetest-a-novel-approach-to-...

[MajimasEyepatch]

From the Hacker News Guidelines: "Please don't complain about tangential annoyances—e.g. article or website formats, name collisions, or back-button breakage. They're too common to be interesting."

https://news.ycombinator.com/newsguidelines.html

[mdaniel]

it also has no license file, with https://github.com/kolodny/safetest/blob/main/package.json#L... saying "MIT" but as far as I know it says that a lot and I doubt gravely that any court would consider a json file a legitimate license declaration

[joks]

Is hitting the (x) on the banner that difficult?