Cypress
Cypress and Jest are not competitors—they test different things. Jest runs in Node.js and tests individual functions, modules, and components in isolation. Cypress runs in a real browser and tests complete user flows end-to-end. The decision isn't "Cypress or Jest"—it'
Testing
Testing real-time event-driven code is one of the more intellectually demanding corners of frontend and Node.js testing. The code is inherently asynchronous, order-dependent, and timing-sensitive. Standard expect(value).toBe(x) assertions are insufficient when the value hasn't arrived yet. This guide covers the
Jest
You've covered jest.fn() and jest.mock(). Now you're staring at a test that needs to control setTimeout, mock an ES module, or stub a class constructor. These are the patterns where Jest's documentation runs thin and Stack Overflow answers contradict each other. Here&
Testing
Snapshot tests are one of those testing tools that developers either overuse or underuse. They get added to every component by default, then blindly updated whenever tests fail — or they get avoided entirely by teams burned by maintenance overhead. The answer is in the middle: snapshot tests are genuinely useful
Testing
Snapshots that start as a safety net often become a maintenance burden. Test files fill with .snap files that nobody reviews. Developers run jest -u reflexively when tests fail. The snapshots grow to thousands of lines covering third-party component internals. This guide covers the practices that keep snapshot tests
Testing
Snapshot testing is one of Jest's most misunderstood features. Used well, it prevents accidental UI regressions with almost zero effort. Used poorly, it becomes a maintenance burden that developers mindlessly update without thinking. This guide covers everything React developers need to know about Jest snapshot testing — from the
Testing
Snapshot testing is one of those features that sounds like a silver bullet — write one line of code, and Jest will catch any unexpected change in your output. In practice, it works brilliantly for some scenarios and creates noise in others. Understanding the mechanism helps you decide when to reach
Test Reliability
When a flaky test blocks your CI pipeline, you have three bad options: delete it (lose the coverage), skip it (test.skip, forget it forever), or fix it immediately (takes time you don't have). The quarantine pattern is the fourth option: isolate it, run it separately, and track
Testing
A slow test suite kills developer flow. When Jest runs 800 tests sequentially it can take 8-12 minutes. With sharding across 4 parallel GitHub Actions runners, that drops to 2-3 minutes — same compute budget, 4× faster feedback. Here's how to set it up. How Jest Sharding
Testing
Electron applications combine Node.js and Chromium into a single runtime, making them powerful but uniquely challenging to test. Unlike pure web apps or pure Node.js services, Electron apps have two processes—main and renderer—that communicate via IPC. Jest is the go-to testing framework for the Node.
Testing
Timezone and locale bugs are notoriously hard to catch: they pass on developer machines and fail in production, or fail in CI only in certain months when DST shifts. This guide covers practical patterns for making timezone and locale-sensitive code testable and deterministic. Mocking Date in Jest The most
Phaser.js
Phaser.js powers thousands of browser games, but testing it is notoriously tricky. The framework depends on browser APIs — WebGL, Canvas, Web Audio, requestAnimationFrame — that don't exist in Node.js. Most teams give up and test manually. This guide shows you a practical approach using Jest with jsdom,