snap-shot-it

library7.9.10jsnpmunverified

snap-shot-it is a snapshot testing utility designed for Mocha and other BDD-style JavaScript test runners. It provides a robust mechanism to capture the output of functions or data structures during test execution and compare them against previously saved snapshots, making it easier to track unintended changes. The current stable version is 7.9.10, released in late 2022, and its release cadence primarily focuses on dependency updates and minor bug fixes, indicating a maintenance-oriented development. A key differentiator is its approach of spying on the global `it` function to precisely determine test context, offering better reliability than static code parsing methods. It integrates `snap-shot-compare` for intelligent, human-readable diffs and supports a data-driven testing mode, which sets it apart from simpler snapshot solutions by offering more advanced testing patterns within the Mocha ecosystem.

testing

npm install snap-shot-it

github ↗package ↗

INSTALL

IMPORT

SIG · SNAP-SHOT-IT

snap-shot-it

testingjavascriptv7.9.10

Install

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Import

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Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

snapshot

✓ const snapshot = require('snap-shot-it')

✗ const { snapshot } = require('snap-shot-it')

The primary export is a default function. Use this pattern for CommonJS modules, typically in Mocha test files.

snapshot

✓ import snapshot from 'snap-shot-it'

✗ import { snapshot } from 'snap-shot-it'

For ES Modules and TypeScript, import the default function. The package provides TypeScript definitions for `snapshot` and its options.

This quickstart demonstrates how to set up `snap-shot-it` with Mocha, showing basic snapshot creation for synchronous values, strings, asynchronous results, and an example of data-driven testing. It includes instructions for running tests and updating snapshots.

/* package.json */ // { // "name": "my-test-project", // "version": "1.0.0", // "devDependencies": { // "mocha": "^10.0.0", // "chai": "^4.0.0", // "snap-shot-it": "7.x.x" // }, // "scripts": { // "test": "mocha --require snap-shot-it spec.js" // } // } /* spec.js */ const snapshot = require('snap-shot-it'); const { expect } = require('chai'); function add(a, b) { return a + b; } describe('My Math Functions', () => { it('adds two numbers correctly', () => { const result = add(5, 7); snapshot(result); // First snapshot will create __snapshots__/spec.js with '12' expect(result).to.equal(12); }); it('handles strings as snapshots', () => { const message = "Hello, snapshot world!"; snapshot(message); // Second snapshot 'Hello, snapshot world!' expect(message).to.be.a('string'); }); it('can snapshot asynchronous results', async () => { const asyncResult = await Promise.resolve({ id: 1, name: 'Async Data', timestamp: new Date('2023-01-01T00:00:00Z') }); snapshot(asyncResult); // Third snapshot with object expect(asyncResult.id).to.equal(1); }); // Data-driven testing example ['foo', 'bar', 'baz'].forEach((value) => { it(`processes value ${value}`, () => { snapshot(`processed-${value}`); // Snapshots will be named "processes value foo 1", "processes value bar 1", etc. }); }); }); // To run: // 1. npm install mocha chai snap-shot-it --save-dev // 2. Add the 'test' script to package.json // 3. Run: npm test // 4. To update snapshots: SNAPSHOT_UPDATE=1 npm test

Debug

Known issues

breakingStarting with version 7.9.1, `snap-shot-it` requires Node.js version 8 or above. Older Node.js versions are no longer supported.

fix

Upgrade your Node.js environment to version 8.x or newer.

affects: >=7.9.1

gotchaWhen using named snapshots (e.g., `snapshot('my name', value)`), the names must be unique within a single spec file by default. Duplicates will lead to unexpected behavior unless explicitly allowed.

fix

Ensure each named snapshot has a unique name per spec file. If intentional sharing is required, pass `{ allowSharedSnapshot: true }` as an option: `snapshot('my shared snapshot', value, { allowSharedSnapshot: true })`.

affects: >=1.0.0

gotchaTo update, dry-run, or view snapshots, you must use specific environment variables (e.g., `SNAPSHOT_UPDATE=1`, `SNAPSHOT_DRY=1`, `SNAPSHOT_SHOW=1`) when running your tests.

fix

Prefix your test command with the desired environment variable, e.g., `SNAPSHOT_UPDATE=1 npm test` to update snapshots.

affects: >=1.0.0

gotcha`snap-shot-it` relies on spying on Mocha's global `it` function to determine test context. This approach, while effective, might cause conflicts or unexpected behavior in highly customized Mocha setups or when combined with other test utilities that also modify global test runner functions.

fix

If conflicts arise, review your test runner configuration and other test utilities to identify potential interactions with global `it` modifications. Consider isolating tests or using alternative snapshot solutions if deep customization is unavoidable.

affects: >=1.0.0

Errors

Common errors & fixes

Error: 42 !== 80

A previously saved snapshot value does not match the current test output, indicating a regression or an intentional change.

fix

Verify if the change is intentional. If it is, run your tests with `SNAPSHOT_UPDATE=1 npm test` to update the snapshot file. Otherwise, fix the code causing the unexpected output.

Cannot read property 'afterAll' of undefined

Running versions of `snap-shot-it` older than 7.9.2 with a test suite where all tests are skipped, which could lead to a crash in the `afterAll` hook.

fix

Upgrade to `snap-shot-it@7.9.2` or newer to resolve the `afterAll` hook crash. Alternatively, ensure at least one test is not skipped.

SyntaxError: Unexpected token 'export' or 'import'

Attempting to use ES Module syntax (`import`) in a CommonJS environment or vice-versa without proper configuration (e.g., `"type": "module"` in `package.json`).

fix

Ensure your project's module system is correctly configured. For CommonJS, use `const snapshot = require('snap-shot-it')`. For ES Modules, use `import snapshot from 'snap-shot-it'` and verify `package.json` specifies `"type": "module"` or files use `.mjs` extensions.

Upgrade

Version history

7.9.10latest on npm

Audit

Dependencies

snap-shot-corerequiredProvides the core logic for loading and saving snapshots.

snap-shot-comparerequiredUsed for intelligent, human-readable diffing when snapshots diverge.

mochaoptionalThe intended test runner for this utility, expected to be installed as a dev dependency in the consuming project.

Agent activity

5 hits · last 30 days

node

Resources

githubhttps://github.com/bahmutov/snap-shot-it ↗

packagehttps://www.npmjs.com/package/snap-shot-it ↗