A snapshot testing utility for Mocha.

This package provides utilities to do Snapshot Testing on Mocha.

Use npm or a compatible tool to install.

npm install mocha-assert-snapshot

Give --require mocha-assert-snapshot option to Mocha.

mocha --require mocha-assert-snapshot -- test/**/*.js

It registers root hooks to read/write snapshots.

Then use assertSnapshot(value) or assertSnapshotThrows(func) in your tests.

import { assertSnapshot, assertSnapshotThrows } from "mocha-assert-snapshot";

it("a snapshot test", () => {
  const actual = doSomething();
  assertSnapshot(actual);
});

it("a snapshot test (async)", async () => {
  const actual = await doSomething();
  assertSnapshot(actual);
});

it("a snapshot test for thrown errors", () => {
  assertSnapshotThrows(() => {
    throw new Error("my error");
  });
});

it("a snapshot test for thrown errors (async)", async () => {
  await assertSnapshotThrows(async () => {
    throw new Error("my error");
  });
});

Of course, it works well along with the --parallel option.

There are two ways to update snapshots.

Giving --update CLI option, it updates snapshots.

mocha --require mocha-assert-snapshot --update -- test/**/*.js

It's nice, but it doesn't work on parallel mode because Mocha doesn't pass the CLI arguments to workers.

Giving MOCHA_ASSERT_SNAPSHOT=update environment variable, it updates snapshots.

MOCHA_ASSERT_SNAPSHOT=update mocha --require mocha-assert-snapshot -- test/**/*.js

If you want to use this way on cross-platform, use cross-env package or something like that.

See GitHub Releases.

Welcome contributing!

Please use GitHub's Issues/PRs.

• npm test runs tests and measures coverage.
• npm run build compiles source code to index.mjs, index.js, index.mjs.map, index.js.map, and index.d.ts.
• npm run clean removes the temporary files which are created by npm test and npm run build.
• npm run format runs Prettier.
• npm run lint runs ESLint.
• npm version <patch|minor|major> makes a new release.