data-snapshot 📸

data-snapshot is a generic mock data manager for JavaScript tests, that helps you use data from real endpoints in tests.

On first run / update, data-snapshot executes the thunk (which returns a promise), and then writes the result of the promise to disk to avoid network calls on subsequent test runs.

A __data_snapshots__ is created adjacent to your test file (similar to Jest's __snapshots__), with the same name as your test file. Mock data is stored within that file.

You can then update your data by rerunning your specs with a --updateSnapshot/-u flag, or by deleting the snapshot file.

Data snapshots should be committed to version control, as regular snapshot files are. The snapshot file is then used in CI.

Installing

npm i --save-dev data-snapshot

Usage

import dataSnapshot from 'data-snapshot';
 
// hits endpoint on first run; resolves from disk on 2nd
const fetchData = id => fetch(`/api/${id}`).then(r => r.json());
 
test('some-spec', async () => {
  const data = await dataSnapshot('key', () => fetchData(1));
  expect(data.a).toBe(true);
});

Expires

The data is never actually expired (to avoid CI unintentionally triggering an Ajax call, etc). However, if you would like to be reminded with a console warning to update your data periodically, set an expires flag.

const ONE_MONTHISH = 1000 * 60 * 60 * 24 * 30;
dataSnapshot('key', thunkPromise, {expires: Date.now() + ONE_MONTHISH});

API

dataSnapshot<D>(
  name: string,
  thunkPromise: () => Promise<D>,
  opts: {expires?: number} = {}
): Promise<D>

--updateSnapshot/-u will re execute your data fetcher (jest --updateSnapshot).

Running the tests

npm test

Built With

• Babel
• Flow
• Jest

Contributing

Please read CODE_OF_CONDUCT.md for details on our Code of Conduct.

To contribute, please open an issue, or submit a pull request with appropriate test coverage.

License

This project is licensed under the BSD-2-Clause license - see the LICENSE.md file for details