Testing
API synthetic monitoring is the most cost-effective monitoring you can do. No browser, no JavaScript, no rendering — just send an HTTP request and validate the response. A well-configured API monitor can run every 30 seconds for minimal cost and catch outages within a minute. This guide covers the full spectrum:
Testing
You've hit 100% code coverage. Every line, every branch, every condition — green. Time to ship with confidence, right? Not quite. Code coverage tells you which lines were executed during tests. It says nothing about whether your tests would catch a bug if one appeared. Mutation testing does. The
Testing
DOM snapshots catch structural changes. Visual snapshot testing catches what DOM snapshots miss: layout shifts, color changes, font rendering differences, and the thousand small things that look fine in code but break in the browser. Percy and Chromatic are the two dominant tools in this space, and they take meaningfully
Testing
Snapshot updates are routine maintenance — but routine doesn't mean thoughtless. The difference between a team that benefits from snapshot testing and one that doesn't comes down to how updates are handled. A careless update covers up a regression. A thoughtful one confirms an intentional change and
Testing
Test-driven development has a reputation as a coding technique. Write a failing test. Write the code to make it pass. Refactor. Repeat. That loop is real and valuable, but it starts too late. By the time a developer opens their editor, the most expensive design decisions have already been made.
Testing
Test interference is one of the subtlest sources of test suite unreliability. Tests that pass in isolation fail when run together. Tests that pass in one order fail in another. A test that worked for six months suddenly starts failing after an unrelated test is added. The cause, almost always,
Testing
Most teams treat test environment provisioning as an operations problem: file a ticket, wait for an engineer to spin something up, hope it matches what you actually need. Infrastructure as Code flips this. When your test environments are defined in Terraform, any team member can provision a complete, correctly configured
Testing
You've seen this failure mode. Tests pass in staging. The deployment goes out. Production breaks. The post-mortem reveals a configuration value that was set differently, a library version that diverged, a database setting that nobody noticed. The staging environment had drifted from production, and your test suite had
Testing
Stryker is the leading mutation testing framework for JavaScript and TypeScript. It supports Jest, Mocha, Jasmine, and Karma — and generates one of the clearest mutation reports available in any language ecosystem. Here's how to set it up and actually use the results. Installation Start by installing the Stryker
Testing
"Snapshot testing" gets used to mean two different things, and conflating them leads to wrong tool choices. DOM snapshot testing captures the HTML structure of a component. Visual regression testing captures what it actually looks like in a browser. These catch different bugs, cost different amounts to maintain,
Testing
React component testing has evolved considerably. Enzyme snapshots gave way to React Testing Library, and the community's view on snapshot testing shifted along with it. The current reality: snapshots aren't obsolete, but their role is more specific than it once was. Understanding what they're
Testing
There's a pattern that plays out on almost every team that adopts snapshot testing. It starts with good intentions: snapshots are easy to create, they run automatically, and they seem to provide coverage. Then a few months later, someone's blocked on a PR review because of