@funktechno/multi-assert

Run a group of assertions in any Node test framework, keep going past failures, and get one readable error that lists every failure. Works with Jest, Vitest, node:test, mocha/chai, Playwright and anything else that throws on a failed assertion. No runtime dependencies.

npm install --save-dev @funktechno/multi-assert

import { multiAssert } from "@funktechno/multi-assert";

multiAssert([
  () => expect(res.status).toBe(200),
  () => expect(res.body.id).toBe(42),
  () => assert.equal(res.headers["content-type"], "application/json"),
]);

2 of 3 assertions failed

  ✕ 1) expected 404 to be 200 // Object.is equality
       → src/api/__tests__/http.spec.ts:38:24

  ✕ 3) Expected values to be strictly equal:
       + actual - expected
       + 'text/html'
       - 'application/json'
       → src/api/__tests__/http.spec.ts:40:14

Call forms

// bare functions
multiAssert([() => a(), () => b()]);

// labelled, as tuples or as an object
multiAssert([["status is 200", () => a()], ["has id", () => b()]]);
multiAssert({ "status is 200": () => a(), "has id": () => b() });

// async checks run in order
await multiAssertAsync([async () => expect(await load()).toBe(1), () => b()]);

multiAssert is synchronous. A check that returns a promise is reported as a failure that tells you to use multiAssertAsync, so a rejected promise is never silently dropped.

Options

Option	Default	Meaning
message	none	Heading shown after the summary line, e.g. "user API response".
rethrowSingle	true	If exactly one check fails, and it has no label and the group has no message, the original error is rethrown so the framework shows its native diff.
color	"auto"	Keep colors only on a color TTY with NO_COLOR and CI unset, so JUnit XML stays clean.
stackFrames	1	Stack frames shown under each failure (0 hides them).
adapters	[]	Custom error adapters, tried before the built-in ones.

Set defaults once, for example in a test setup file: configure({ stackFrames: 0 }).

The error

Two or more failures throw a MultiAssertError (an AggregateError):

• errors: the original errors, untouched, so instanceof, actual and expected survive;
• failures: { index, label?, message, actual?, expected?, operator?, location? }[];
• passed and total counts;
• toJSON() returns { name, message, passed, total, failures }. failures, passed and total are non-enumerable so reporters that dump an error's own properties (Vitest) do not print them twice.

The first line of the message is a short summary because JUnit message attributes and CI annotation titles usually show only that. error.stack points at the call to multiAssert, so reporter code frames land in your test.

Custom adapters

Built in: expect matcher results (Jest, Vitest, Playwright), node:assert, chai, plain Error and non-Error throws. For an in-house assertion library:

multiAssert(checks, {
  adapters: [
    {
      matches: (e) => e instanceof MyAssertError,
      normalize: (e) => ({ message: (e as MyAssertError).detail }),
    },
  ],
});

Jest matcher

import "@funktechno/multi-assert/jest" (or installMultiAssertMatchers(expect)) adds expect(value).toPassAll([...]), where each check receives value:

expect(res).toPassAll([
  ["status", (r) => expect(r.status).toBe(200)],
  ["id", (r) => expect(r.body.id).toBe(42)],
]);

Types for the subpath need moduleResolution node16, nodenext or bundler.

Development

npm ci
npm run lint
npm test
npm run build

MIT