API contract, and rudimentary tests, for modules that conform to the *es-shim API*
The es-shim API project defines a standardized contract and test suite for JavaScript polyfill packages that implement ECMAScript specifications. It specifies required entry points such as `polyfill`, `shim`, and `auto`, along with invariants for how compliant packages must behave across different environments—including ES3 and later browsers, Node.js, and Web Workers. The project provides a binary tool for validating that packages follow the es-shim API contract, and recommends using related packages like es-abstract, define-properties, and call-bind to ensure spec compliance and robustness against environment modification. It is maintained by the es-shims organization on GitHub.