node:assert

node:assert and node:assert/strict provide Node’s assertion functions, from ok and deepStrictEqual to throws, rejects, match and partialDeepStrictEqual.

Example

// assert.mjs
import assert from "node:assert/strict";

assert.deepEqual({ ids: [1, 2] }, { ids: [1, 2] });
assert.throws(() => JSON.parse("{"), SyntaxError);
await assert.rejects(Promise.reject(new Error("nope")), /nope/);

try {
  assert.equal(1 + 1, 3);
} catch (error) {
  console.log(error.name, error.code, error.actual, error.expected);
}

utf-8 · js · Lines: 12

elide run assert.mjs prints:

text

AssertionError ERR_ASSERTION 2 3

utf-8 · text · Lines: 1

Differences from Node

assert.Assert is not a constructor.
Loose deepEqual treats null and undefined as different, and compares proxies differently.
A symbol message, or a number as expected in throws(), raises AssertionError instead of ERR_INVALID_ARG_TYPE.
AssertionError.operator holds the method name (strictEqual), not a symbol (===).

Reference

Status: Partial · 7 of 13 suite tests pass (53.8%) · since 1.1.0

Exports

Export	Kind	Status	Notes
`ok()`	function	Full	Tests if `value` is truthy
`equal()`	function	Full	Tests shallow equality between `actual` and `expected` using `==`
`notEqual()`	function	Full	Tests shallow inequality between `actual` and `expected` using `!=`
`strictEqual()`	function	Full	Tests strict equality between `actual` and `expected` using `===`
`notStrictEqual()`	function	Full	Tests strict inequality between `actual` and `expected` using `!==`
`deepEqual()`	function	Full	Tests for deep equality between `actual` and `expected` using abstract equality (`==`) for leaf comparisons
`deepStrictEqual()`	function	Full	Tests for deep strict equality between `actual` and `expected` using strict equality (`===`) for leaf…
`notDeepEqual()`	function	Full	Tests that `actual` is NOT deeply equal to `expected` (abstract equality)
`notDeepStrictEqual()`	function	Full	Tests that `actual` is NOT deeply strictly equal to `expected`
`throws()`	function	Full	Expects the function `fn` to throw an error
`doesNotThrow()`	function	Full	Asserts that the function `fn` does not throw an error
`rejects()`	function	Full	Awaits the `asyncFn` promise (or calls it if it’s a function) and expects it to reject
`doesNotReject()`	function	Full	Awaits the `asyncFn` promise (or calls it if it’s a function) and expects it NOT to reject
`fail()`	function	Full	Throws an AssertionError unconditionally
`ifError()`	function	Full	If `value` is truthy (not null/undefined/false), throws it
`match()`	function	Full	Expects `string` to match the regular expression `regexp`
`doesNotMatch()`	function	Full	Expects `string` NOT to match the regular expression `regexp`

Not implemented

Assert, assert/strict.Assert.

Tests: node-api node:assert: 7 pass, 6 fail, 0 error, 1 skipped. Failing: test-assert-async.js, test-assert-class-destructuring.js, test-assert-class.js, test-assert-deep.js, test-assert-esm-cjs-message-verify.js, test-assert.js.