assert

Note

To enable built-in Node.js APIs and polyfills, add the nodejs_compat compatibility flag to your Wrangler configuration file. This also enables nodejs_compat_v2 as long as your compatibility date is 2024-09-23 or later. Learn more about the Node.js compatibility flag and v2.

The assert module in Node.js provides a number of useful assertions that are useful when building tests.

import { strictEqual, deepStrictEqual, ok, doesNotReject } from "node:assert";

strictEqual(1, 1); // ok!
strictEqual(1, "1"); // fails! throws AssertionError

deepStrictEqual({ a: { b: 1 } }, { a: { b: 1 } }); // ok!
deepStrictEqual({ a: { b: 1 } }, { a: { b: 2 } }); // fails! throws AssertionError

ok(true); // ok!
ok(false); // fails! throws AssertionError

await doesNotReject(async () => {}); // ok!
await doesNotReject(async () => {
  throw new Error("boom");
}); // fails! throws AssertionError

Note

In the Workers implementation of assert, all assertions run in, what Node.js calls, the strict assertion mode. In strict assertion mode, non-strict methods behave like their corresponding strict methods. For example, deepEqual() will behave like deepStrictEqual().

Refer to the Node.js documentation for assert ↗ for more information.