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This is Part 14 of the “Frontend Testing, Done Right” series. Browse the full series · Glossary “Works on my machine, red on CI.” The homework of everyone who operates E2E, and the prime cause of console.log wallpaper. Playwright ships three tools that solve this mystery with evidence: traces that rewind the failure whole, a UI mode that time-travels, and retries used as a signal. We pack all three today. Series readers: this is insurance for the day your E2E breaks. Searchers: this is the emergency kit for the test that’s broken right now. Examples are self-contained. ...

This is Part 13 of the “Frontend Testing, Done Right” series. Browse the full series · Glossary Past ten E2E tests, two things start to hurt: the setup code copy-pasted into every test, and the suite slowing down as it runs in sequence. Playwright’s fixtures (a mechanism that injects repeated setup into tests) and parallel execution solve both at once — this article covers custom fixtures, auth reuse (storageState), and the safety rules for parallelism. ...

I had clearly written a dark gray into my CSS. color: #595959. On a white background that color has a contrast of 6.4:1, which comfortably clears the accessibility bar of 4.5:1. Pass. Then I ran an accessibility checker, and a red line appeared. This text has a contrast of 4.04:1, which is insufficient. Expected ratio: 4.5:1. I put in a color that measures 6.4:1, so why is it calling it 4:1? Was the checker wrong? ...

This is Part 12 of the “Frontend Testing, Done Right” series. Browse the full series · Glossary Flaky tests — the code hasn’t changed, yet some days it passes and some days it fails. It’s the first illness every team catches when adopting E2E, and left untreated it breeds a scary culture: “that one again? just rerun it.” Fortunately the cause is usually singular: finding elements too early, or the wrong way. This article pulls that root out with Playwright’s locators and auto-wait. ...

Some people set their screen to maximum contrast. Yellow text on black, white text on blue, that sort of thing. For low-vision users this is the difference between being able to read the text and not; people with migraines or light sensitivity go the other way, using a muted, low-contrast palette. They have one thing in common — the user decides the colors. And the moment they do, a good chunk of the colors we wrote in CSS get ignored. ...

I turned on dark mode and my eyes hurt more. The background was black but the text was a heavy gray, so the contrast was far too low; links were still the default blue (#0000ff), which stung. Images blazed alone against the dark screen. One button was the same color as its background, so it was simply invisible. It said “dark mode supported.” But it was dark mode by color inversion, nothing more. ...

This is Part 11 of the “Frontend Testing, Done Right” series. Browse the full series · Glossary Playwright is an E2E testing tool that drives real browsers (Chromium, Firefox, WebKit) with code. E2E (End-to-End) is exactly what it says — reproducing the entire flow of a user visiting, searching, and seeing results, in an actual browser. This article goes from install to a passing first scenario in one sitting. If you’ve been following the series, this is where the stage gets bigger — we’ve been playing inside jsdom, a pretend browser; now we open a real one. New here? No problem: we start from installation, and you can put any Vite/React app of yours where the demo app sits. (Demo UI strings are Korean — 대시보드 = “Dashboard”, 검색 = “Search”.) ...

This is Part 10 of the “Frontend Testing, Done Right” series. Browse the full series · Glossary What comes to mind when you hear “accessibility testing”? Hiring a consultant, adopting a dedicated audit tool, working through checklists hundreds of items long… it’s easy to picture something big. Surprisingly, though, half of accessibility verification comes free just from writing component tests well. This article is that principle plus the practice — flushing out div buttons, naming icon buttons, and guarding focus that vanishes into thin air. ...

Running a quiz service, we got a complaint one day: “I just took the test — why does it say ‘No score’?” We checked. Their score was zero. The database clearly stored 0, the API returned 0 faithfully. The culprit was a single line in the UI code. javascript Read line numbers: OFF Line-number reading help Reading line numbers aloud This button is for screen reader users. ...

This is Part 9 of the “Frontend Testing, Done Right” series. Browse the full series · Glossary The moment a component starts calling an API, tests get shaky. A slow server makes them slow, changed data breaks them, and offline they’re wiped out. MSW (Mock Service Worker) intercepts network requests at the boundary and returns prepared responses, solving the problem at its root. This one article covers installation, handlers, and simulating both success and failure. ...