SetupFiles

SetupFiles is a configuration option used by Jest, the JavaScript testing framework. It specifies an array of module paths that are loaded before each test file is executed. The intent is to polyfill or configure global state so tests can run in a consistent environment, without relying on per-test boilerplate.

Files listed in setupFiles are loaded before the test framework is installed, and they run in the test environment in the order given. They typically contain global polyfills, mocks, or other global shims. They can be specified in Jest configuration either in package.json under the jest field or in a dedicated jest.config.js, for example: setupFiles: ['<rootDir>/src/setupEnv.js'].

Unlike setupFilesAfterEnv, which runs after the test framework has been set up, setupFiles is meant for pre-environment configuration. Use it for polyfills or to establish globals that tests need across the suite. Be mindful that setupFiles should not use Jest APIs, since the test framework may not be fully initialized at that time.