assert

Warning

To use Node.js APIs in your Worker, add the nodejs_compat_v2 compatibility flag to your wrangler.toml file.

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.