Skip to content

Commit

Permalink
feat: roll v28 docs (#12733)
Browse files Browse the repository at this point in the history
  • Loading branch information
SimenB authored Apr 25, 2022
1 parent e9f6610 commit c79f8d6
Show file tree
Hide file tree
Showing 40 changed files with 10,666 additions and 2 deletions.
6 changes: 5 additions & 1 deletion package.json
Original file line number Diff line number Diff line change
Expand Up @@ -132,7 +132,11 @@
}
},
{
"files": "lerna.json",
"files": [
"lerna.json",
"website/sidebars.json",
"website/versioned_sidebars/*.json"
],
"options": {
"parser": "json-stringify"
}
Expand Down
4 changes: 3 additions & 1 deletion website/sidebars.json
Original file line number Diff line number Diff line change
Expand Up @@ -33,7 +33,9 @@
"tutorial-react-native",
"testing-frameworks"
],
"Upgrade Guides": ["upgrading-to-jest28"]
"Upgrade Guides": [
"upgrading-to-jest28"
]
},
"api": [
"api",
Expand Down
16 changes: 16 additions & 0 deletions website/versioned_docs/version-28.0/Architecture.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
---
id: architecture
title: Architecture
---

import LiteYouTubeEmbed from 'react-lite-youtube-embed';

If you are interested in learning more about how Jest works, understand its architecture, and how Jest is split up into individual reusable packages, check out this video:

<LiteYouTubeEmbed id="3YDiloj8_d0" />

If you'd like to learn how to build a testing framework like Jest from scratch, check out this video:

<LiteYouTubeEmbed id="B8FbUK0WpVU" />

There is also a [written guide you can follow](https://cpojer.net/posts/building-a-javascript-testing-framework). It teaches the fundamental concepts of Jest and explains how various parts of Jest can be used to compose a custom testing framework.
58 changes: 58 additions & 0 deletions website/versioned_docs/version-28.0/BypassingModuleMocks.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,58 @@
---
id: bypassing-module-mocks
title: Bypassing module mocks
---

Jest allows you to mock out whole modules in your tests, which can be useful for testing if your code is calling functions from that module correctly. However, sometimes you may want to use parts of a mocked module in your _test file_, in which case you want to access the original implementation, rather than a mocked version.

Consider writing a test case for this `createUser` function:

```javascript title="createUser.js"
import fetch from 'node-fetch';

export const createUser = async () => {
const response = await fetch('http://website.com/users', {method: 'POST'});
const userId = await response.text();
return userId;
};
```

Your test will want to mock the `fetch` function so that we can be sure that it gets called without actually making the network request. However, you'll also need to mock the return value of `fetch` with a `Response` (wrapped in a `Promise`), as our function uses it to grab the created user's ID. So you might initially try writing a test like this:

```javascript
jest.mock('node-fetch');

import fetch, {Response} from 'node-fetch';
import {createUser} from './createUser';

test('createUser calls fetch with the right args and returns the user id', async () => {
fetch.mockReturnValue(Promise.resolve(new Response('4')));

const userId = await createUser();

expect(fetch).toHaveBeenCalledTimes(1);
expect(fetch).toHaveBeenCalledWith('http://website.com/users', {
method: 'POST',
});
expect(userId).toBe('4');
});
```

However, if you ran that test you would find that the `createUser` function would fail, throwing the error: `TypeError: response.text is not a function`. This is because the `Response` class you've imported from `node-fetch` has been mocked (due to the `jest.mock` call at the top of the test file) so it no longer behaves the way it should.

To get around problems like this, Jest provides the `jest.requireActual` helper. To make the above test work, make the following change to the imports in the test file:

```javascript
// BEFORE
jest.mock('node-fetch');
import fetch, {Response} from 'node-fetch';
```

```javascript
// AFTER
jest.mock('node-fetch');
import fetch from 'node-fetch';
const {Response} = jest.requireActual('node-fetch');
```

This allows your test file to import the actual `Response` object from `node-fetch`, rather than a mocked version. This means the test will now pass correctly.
Loading

0 comments on commit c79f8d6

Please sign in to comment.