Every Testing Library test you have written runs against a simulated DOM. You know this. You accepted it years ago, along with the small pile of things that come with it: no real layout, nothing ever drawn on a screen, jsdom throwing on APIs it does ...

You open a frontend pull request. The diff is 400 lines, an AI agent wrote most of it, and the description says "adds the checkout flow". CI is green. You read the diff. It looks reasonable. You still have no idea what the UI actually does. So you ...

Not every app has a bundler. Plenty of real software is still a folder of HTML and JavaScript served as static files: internal tools, landing pages, small products, and anything deliberately kept simple. These apps ship and they matter, but their tes...

Automated accessibility testing usually means one thing: point a scanner at the page, let it check the initial HTML against a set of WCAG rules, and turn green. Missing alt text, an unlabeled input, low-contrast text at load. Caught. Done. Then a us...

Payment integrations are one of the hardest things to test in a web app. The SDK renders its own UI, controls its own form fields, and fires callbacks when the user completes a payment. You can't programmatically fill in a credit card number. You can...

The first time you try to test a TanStack app the way the React Testing Library docs suggest, the test file gets bigger than the component. You spin up a memory router, instantiate a new QueryClient per test, wrap everything in QueryClientProvider an...

One of the biggest milestones we’ve been working on is now live: TWD 1.3.x brings full multi-framework support with a single unified setup. This means you can now drop TWD into React, Vue, Solid, and Angular projects using the exact same initializat...

In Part 2https://coderlegion.com/7371/testing-while-developing-part-2-selectors-assertions-and-user-events, we explored assertions, selectors, and user interactions in TWD. We used those tools to test the homepage, which only had a single button. N...

TWD still has many more advanced features — such as function mocking — but with what we’ve covered so far, you already have everything a solid testing tool needs. In this step, we’ll see how to collect code coverage from your TWD tests and visualize ...

In this part, we’ll look at a new feature in TWD: support for Testing Library–style selectors. These selectors are widely known in the community, and while you could technically use them before TWD is very flexible, now they’re fully integrated — inc...

In the previous posthttps://coderlegion.com/7370/testing-while-developing-part-1-installation-and-first-test, we set up our basic testing configuration and used the visit command to load our app. Now, we’re ready to make our tests a little more meani...

We continue with the sixth part of this series on React Router Data Mode. This time, we'll talk about actions: one of the key pieces for data handling that React Router offers. If you're coming from the previous posthttps://coderlegion.com/4297/rea...

Let's move on to the third part of this tutorial series. In this case, we'll look at a concept that comes from Remix and can now also be found in React Router: loaders. If you're coming from the previous tutorialhttps://coderlegion.com/3682/react-ro...

TypeScript’s utility types give you powerful ways to transform and manipulate existing types. If you’ve already used types like Partial or Pick, it’s time to expand your toolbox. In this article, we'll focus on five highly useful utility types: O...

If you're reading this, you're probably working with React or learning how to use it. And if that’s the case, you’ve surely heard of react-router, the most popular library for routing in React apps for years. But what you may not know is that in its...