Node.js Test Runner - expect().toMatchSnapshot() integration

Node.js Test Runner is great, Expect is great, Snapshots are great.

But using them all together at the moment is ... not so great.

This package aims to provide an easy approach to use .toMatchSnapshot with Node.js Test Runner.

Install

yarn add @onigoetz/ntr-expect-snapshot expect

Usage

import { test } from "node:test";

import initializeSnapshot from "@onigoetz/ntr-expect-snapshot";
import { expect } from "expect";

initializeSnapshot(import.meta.url);

test("a snapshot", async () => {
  const response = await fetch("http://example.com");
  const actual = await response.text();

  expect(actual).toMatchSnapshot();
});

Updating snapshots

Updating snapshots is enabled if the --test-update-snapshots (Possible statring with Node.js 22.3.0) flag is passed or the SNAPSHOT_UPDATE environment variable is set to "true"

Shortcomings

Snapshot management is usually tightly integrated within the test runner to offer features such as partial updates when tests are skipped or removing snapshot files when they're no longer needed.

This package can't be integrated tightly with Node.js test runner and here are some things that will probably not be possible to implement:

Remove a snapshot file if the test file is deleted

We are only aware of the current running test files, not other test files so we don't know which other files are or are not present

Remove a snapshot after a test is removed

The fact that a snapshot isn't used in a test run can be due to the test being currently skipped, or tests being filtered. For this reason we can't decide to remove all snapshots for a test at this stage.

Credits / Previous work in the domain

The initial implementation is for most parts a fork of AVA's implementation.

I also checked how other tools in the space work to build a coherent approach

• snap-shot-core
• @matteo.collina/snap
• jest-snapshot