SYSTEM Cited by 2 sources
Jest¶
What it is¶
Jest is a JavaScript testing framework originally developed
by Meta (Facebook). It bundles a test runner, an assertion
library (expect(...)), and mocking / coverage / snapshot
infrastructure. Jest is the de-facto default test runner for
React ecosystems — Enzyme and
RTL both layer on top of it.
Seen in¶
- sources/2024-06-19-slack-ai-powered-conversion-from-enzyme-to-react-testing-library
— Slack's 15,000+ Enzyme tests run under Jest. Custom Jest
matchers (documented in the codemod's prompt as augmented
matchers with
DOMsuffix:toBeCheckedDOM,toBeDisabledDOM,toHaveStyleDOM,toHaveValueDOM) existed to avoid name collisions between Enzyme and RTL matchers during the migration window. Jest'sexpect.getState() .currentTestNamewas the hook used to key per-test-case DOM captures (see concepts/dom-context-injection-for-llm). - sources/2025-01-07-slack-automated-accessibility-testing-at-slack
— Jest appears as the blocker to one attempted
integration path for Slack's Axe accessibility checks.
Slack explored wrapping RTL's
rendermethod to auto-run Axe on every render, but "Running accessibility checks through a separate Jest configuration worked, but would require developers to write tests specifically for accessibility, which we wanted to avoid. Reworking our custom Jest setup was deemed too tricky and not worth the time and resource investment" — so Slack pivoted to Playwright-based integration via fixture extension. Canonical wiki datum for how heavily-customised Jest configurations can close off framework-integration approaches that would work in a vanilla setup.