Skip to content
New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

docs: add upgrading guide #12633

Merged
merged 5 commits into from
Apr 18, 2022
Merged
Show file tree
Hide file tree
Changes from all commits
Commits
File filter

Filter by extension

Filter by extension

Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
1 change: 1 addition & 0 deletions CHANGELOG.md
Original file line number Diff line number Diff line change
Expand Up @@ -85,6 +85,7 @@
- `[docs, examples]` Update React examples to match with the new React guidelines for code examples ([#12217](https://github.com/facebook/jest/pull/12217))
- `[docs]` Add clarity for module factory hoisting limitations ([#12453](https://github.com/facebook/jest/pull/12453))
- `[docs]` Add more information about how code transformers work ([#12407](https://github.com/facebook/jest/pull/12407))
- `[docs]` Add upgrading guide ([#12633](https://github.com/facebook/jest/pull/12633))
- `[expect]` [**BREAKING**] Remove support for importing `build/utils` ([#12323](https://github.com/facebook/jest/pull/12323))
- `[expect]` [**BREAKING**] Migrate to ESM ([#12344](https://github.com/facebook/jest/pull/12344))
- `[expect]` [**BREAKING**] Snapshot matcher types are moved to `@jest/expect` ([#12404](https://github.com/facebook/jest/pull/12404))
Expand Down
184 changes: 184 additions & 0 deletions docs/UpgradingToJest28.md
Original file line number Diff line number Diff line change
@@ -0,0 +1,184 @@
---
id: upgrading-to-jest28
title: From v27 to v28
---

Upgrading Jest from v27 to v28? This guide aims to help refactoring your configuration and tests.

:::info

See [changelog](https://github.com/facebook/jest/blob/main/CHANGELOG.md) for the full list of changes.

:::

## Compatibility

The supported Node versions are 12.13, 14.15, 16.13 and above.

If you plan to use type definitions of Jest (or any of its packages), make sure to install TypeScript version 4.3 or above.

## Configuration Options

### `extraGlobals`

The `extraGlobals` option was renamed to [`sandboxInjectedGlobals`](Configuration.md#sandboxinjectedglobals-arraystring):

```diff
- extraGlobals: ['Math']
+ sandboxInjectedGlobals: ['Math']
```

### `timers`

The `timers` option was renamed to [`fakeTimers`](Configuration.md#faketimers-object). See [Fake Timers](#fake-timers) section bellow for details.

### `testURL`

The `testURL` option is removed. Now you should use [`testEnvironmentOptions`](Configuration.md#testenvironmentoptions-object) to pass `url` option to JSDOM environment:

```diff
- testURL: 'https://jestjs.io'
+ testEnvironmentOptions: {
+ url: 'https://jestjs.io'
+ }
```

## Fake Timers

Fake timers were refactored to allow passing options to the underlying [`@sinonjs/fake-timers`](https://github.com/sinonjs/fake-timers).

### `fakeTimers`

The `timers` configuration option was renamed to [`fakeTimers`](Configuration.md#faketimers-object) and now takes an object with options:

```diff
- timers: 'real'
+ fakeTimers: {
+ enableGlobally: false
+ }
```

```diff
- timers: 'fake'
+ fakeTimers: {
+ enableGlobally: true
+ }
```

```diff
- timers: 'modern'
+ fakeTimers: {
+ enableGlobally: true
+ }
```

```diff
- timers: 'legacy'
+ fakeTimers: {
+ enableGlobally: true,
+ legacyFakeTimers: true
+ }
```

### `jest.useFakeTimers()`

An object with options now should be passed to [`jest.useFakeTimers()`](JestObjectAPI.md#jestusefaketimersfaketimersconfig) as well:

```diff
- jest.useFakeTimers('modern')
+ jest.useFakeTimers()
```

```diff
- jest.useFakeTimers('legacy')
+ jest.useFakeTimers({
+ legacyFakeTimers: true
+ })
```

If legacy fake timers are enabled in Jest config file, but you would like to disable them in a particular test file:

```diff
- jest.useFakeTimers('modern')
+ jest.useFakeTimers({
+ legacyFakeTimers: false
+ })
```

## Test Environment

### Custom Environment

The constructor of [test environment](Configuration.md#testenvironment-string) class now receives an object with Jest's `globalConfig` and `projectConfig` as its first argument. The second argument is now mandatory.

```diff
class CustomEnvironment extends NodeEnvironment {
- constructor(config) {
- super(config);
+ constructor({globalConfig, projectConfig}, context) {
+ super({globalConfig, projectConfig}, context);
+ const config = projectConfig;
```

### `jsdom`

If you are using JSDOM [test environment](Configuration.md#testenvironment-string), `jest-environment-jsdom` package now must be installed separately:

```bash npm2yarn
npm install --save-dev jest-environment-jsdom
```

## Test Runner

If you are using Jasmine [test runner](Configuration.md#testrunner-string), `jest-jasmine2` package now must be installed separately:

```bash npm2yarn
npm install --save-dev jest-jasmine2
```

## Transformer

`process()` and `processAsync()` methods of a custom [transformer module](CodeTransformation.md) cannot return a string anymore. They must always return an object:

```diff
process(sourceText, sourcePath, options) {
- return `module.exports = ${JSON.stringify(path.basename(sourcePath))};`;
+ return {
+ code: `module.exports = ${JSON.stringify(path.basename(sourcePath))};`,
+ };
}
```

## TypeScript

:::info

The TypeScript examples from this page will only work as document if you import `jest` from `'@jest/globals'`:
Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I assume @types/jest will be updated. Something about "until @types/jest@28 is released"?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Yes, updating @types/jest would be the best. I just think, if that will be fixed, we will be adding it upgrading guide. Sort-of: "you should use this version of @types/jest". So this note will disappear naturally. Perhaps?

Copy link
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

Reasonable 👍


```ts
import {jest} from '@jest/globals';
```

:::

### `jest.fn()`

`jest.fn()` now takes only one generic type argument. See [Mock Functions API](MockFunctionAPI.md) page for more usage examples.

```diff
import add from './add';
- const mockAdd = jest.fn<ReturnType<typeof add>, Parameters<typeof add>>();
+ const mockAdd = jest.fn<typeof add>();
```

```diff
- const mock = jest.fn<number, []>()
+ const mock = jest.fn<() => number>()
.mockReturnValue(42)
.mockReturnValueOnce(12);

- const asyncMock = jest.fn<Promise<string>, []>()
+ const asyncMock = jest.fn<() => Promise<string>>()
.mockResolvedValue('default')
.mockResolvedValueOnce('first call');
```
3 changes: 2 additions & 1 deletion website/sidebars.json
Original file line number Diff line number Diff line change
Expand Up @@ -32,7 +32,8 @@
"tutorial-react",
"tutorial-react-native",
"testing-frameworks"
]
],
"Upgrade Guides": ["upgrading-to-jest28"]
},
"api": [
"api",
Expand Down