collectCoverageFrom

collectCoverageFrom is a configuration option used by JavaScript testing tools such as Jest to determine which source files should be included when generating test coverage reports. It defines the set of files from which code coverage data will be collected, allowing developers to focus on relevant parts of the codebase.

The option accepts an array of glob patterns. Patterns can include wildcards and can be negated with a leading exclamation mark to exclude files. Patterns are evaluated relative to the project root. Common usage includes including all source files while excluding tests, mocks, or build artifacts, for example: ["src/**/*.{js,ts,jsx,tsx}", "!src/**/*.test.{ts,tsx}", "!src/**/__tests__/**"].

collectCoverageFrom works in tandem with collectCoverage and coverage-related settings such as coverageDirectory and coverageReporters. When collectCoverage is enabled, only files matched by collectCoverageFrom contribute to the reported coverage. If a file is not matched, or is explicitly excluded, it will not appear in coverage results. To further refine results, you can also use coveragePathIgnorePatterns to hide specific paths from coverage reporting entirely.

Typical use cases include focusing coverage on publishable source code in a library, or excluding configuration and utility files from coverage statistics. Care should be taken to ensure patterns accurately reflect desired files to avoid misleading coverage metrics.