snapshot-assertion

Asserts a string matches a snapshot saved in a file. An environment variable can be used to save rather than assert snapshots.

Installation

To install snapshot-assertion with npm, run:

npm install snapshot-assertion --save-dev

Then, import and use the function assertSnapshot.

Examples

A snapshot assertion in a test-director test:

import fetch from "node-fetch";
import assertSnapshot from "snapshot-assertion";
import TestDirector from "test-director";

const tests = new TestDirector();

tests.add("Get a todo.", async () => {
  const response = await fetch("https://jsonplaceholder.typicode.com/todos/1");
  await assertSnapshot(await response.json(), "snapshots/todo.json");
});

tests.run();

Using the SAVE_SNAPSHOTS environment variable to save snapshots when running a package script:

SAVE_SNAPSHOTS=1 npm run test

Requirements

Supported runtime environments:

• Node.js versions ^16.9.0 || >= 18.0.0.

Projects must configure TypeScript to use types from the ECMAScript modules that have a // @ts-check comment:

• compilerOptions.allowJs should be true.
• compilerOptions.maxNodeModuleJsDepth should be reasonably large, e.g. 10.
• compilerOptions.module should be "node16" or "nodenext".

Exports

The npm package snapshot-assertion features optimal JavaScript module design. These ECMAScript modules are exported via the package.json field exports:

• assertSnapshot.mjs