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测试

测试可帮助你编写和维护代码并防止回归。测试框架可以帮助你实现这一点,允许你描述有关代码应如何表现的断言或期望。Svelte 不会干涉你使用哪种测试框架 — 你可以使用 VitestJasmineCypressPlaywright 等解决方案编写单元测试、集成测试和端到端测试。

¥Testing helps you write and maintain your code and guard against regressions. Testing frameworks help you with that, allowing you to describe assertions or expectations about how your code should behave. Svelte is unopinionated about which testing framework you use — you can write unit tests, integration tests, and end-to-end tests using solutions like Vitest, Jasmine, Cypress and Playwright.

使用 Vitest 进行单元和集成测试(Unit and integration testing using Vitest)

¥Unit and integration testing using Vitest

单元测试允许你测试代码的小部分隔离部分。集成测试允许你测试应用的各个部分,以查看它们是否可以协同工作。如果你使用的是 Vite(包括通过 SvelteKit),我们建议使用 Vitest

¥Unit tests allow you to test small isolated parts of your code. Integration tests allow you to test parts of your application to see if they work together. If you’re using Vite (including via SvelteKit), we recommend using Vitest.

要开始,请安装 Vitest:

¥To get started, install Vitest:

npm install -D vitest

然后调整你的 vite.config.js

¥Then adjust your vite.config.js:

vite.config
import { function defineConfig(config: UserConfig): UserConfig (+3 overloads)defineConfig } from 'vitest/config';

export default function defineConfig(config: UserConfig): UserConfig (+3 overloads)defineConfig({
	// ...
	// Tell Vitest to use the `browser` entry points in `package.json` files, even though it's running in Node
	
UserConfig.resolve?: (ResolveOptions & {
    alias?: AliasOptions;
}) | undefined

Configure resolver

resolve
: var process: NodeJS.Processprocess.NodeJS.Process.env: NodeJS.ProcessEnv

The process.env property returns an object containing the user environment. See environ(7).

An example of this object looks like:

{
  TERM: 'xterm-256color',
  SHELL: '/usr/local/bin/bash',
  USER: 'maciej',
  PATH: '~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin',
  PWD: '/Users/maciej',
  EDITOR: 'vim',
  SHLVL: '1',
  HOME: '/Users/maciej',
  LOGNAME: 'maciej',
  _: '/usr/local/bin/node'
}

It is possible to modify this object, but such modifications will not be reflected outside the Node.js process, or (unless explicitly requested) to other Worker threads. In other words, the following example would not work:

node -e 'process.env.foo = "bar"' && echo $foo

While the following will:

import { env } from 'node:process';

env.foo = 'bar';
console.log(env.foo);

Assigning a property on process.env will implicitly convert the value to a string. This behavior is deprecated. Future versions of Node.js may throw an error when the value is not a string, number, or boolean.

import { env } from 'node:process';

env.test = null;
console.log(env.test);
// => 'null'
env.test = undefined;
console.log(env.test);
// => 'undefined'

Use delete to delete a property from process.env.

import { env } from 'node:process';

env.TEST = 1;
delete env.TEST;
console.log(env.TEST);
// => undefined

On Windows operating systems, environment variables are case-insensitive.

import { env } from 'node:process';

env.TEST = 1;
console.log(env.test);
// => 1

Unless explicitly specified when creating a Worker instance, each Worker thread has its own copy of process.env, based on its parent thread’s process.env, or whatever was specified as the env option to the Worker constructor. Changes to process.env will not be visible across Worker threads, and only the main thread can make changes that are visible to the operating system or to native add-ons. On Windows, a copy of process.env on a Worker instance operates in a case-sensitive manner unlike the main thread.

@sincev0.1.27
env
.string | undefinedVITEST
? { ResolveOptions.conditions?: string[] | undefinedconditions: ['browser'] } : var undefinedundefined });

如果不希望加载所有软件包的浏览器版本,因为(例如)你还测试后端库,你可能需要求助于别名配置

¥[!NOTE] If loading the browser version of all your packages is undesirable, because (for example) you also test backend libraries, you may need to resort to an alias configuration

你现在可以在 .js/.ts 文件中为代码编写单元测试:

¥You can now write unit tests for code inside your .js/.ts files:

multiplier.svelte.test
import { function flushSync(fn?: (() => void) | undefined): void

Synchronously flushes any pending state changes and those that result from it.

flushSync
} from 'svelte';
import { const expect: ExpectStaticexpect, const test: TestAPI

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
} from 'vitest';
import { import multipliermultiplier } from './multiplier.svelte.js'; test<object>(name: string | Function, fn?: TestFunction<object> | undefined, options?: number | TestOptions): void (+2 overloads)

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
('Multiplier', () => {
let let double: anydouble = import multipliermultiplier(0, 2); expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)expect(let double: anydouble.value).JestAssertion<any>.toEqual: <number>(expected: number) => voidtoEqual(0); let double: anydouble.set(5); expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)expect(let double: anydouble.value).JestAssertion<any>.toEqual: <number>(expected: number) => voidtoEqual(10); });
multiplier.svelte
/**

 * @param {number} initial

 * @param {number} k
 */
export function 
function multiplier(initial: number, k: number): {
    readonly value: number;
    set: (c: number) => void;
}
@paraminitial
@paramk
multiplier
(initial: number
@paraminitial
initial
, k: number
@paramk
k
) {
let let count: numbercount =
function $state<number>(initial: number): number (+1 overload)
namespace $state

Declares reactive state.

Example:

let count = $state(0);

https://svelte.dev/docs/svelte/$state

@paraminitial The initial value
$state
(initial: number
@paraminitial
initial
);
return { get value: numbervalue() { return let count: numbercount * k: number
@paramk
k
;
}, /** @param {number} c */ set: (c: number) => void
@paramc
set
: (c: number
@paramc
c
) => {
let count: numbercount = c: number
@paramc
c
;
} }; }
export function 
function multiplier(initial: number, k: number): {
    readonly value: number;
    set: (c: number) => void;
}
multiplier
(initial: numberinitial: number, k: numberk: number) {
let let count: numbercount =
function $state<number>(initial: number): number (+1 overload)
namespace $state

Declares reactive state.

Example:

let count = $state(0);

https://svelte.dev/docs/svelte/$state

@paraminitial The initial value
$state
(initial: numberinitial);
return { get value: numbervalue() { return let count: numbercount * k: numberk; }, set: (c: number) => voidset: (c: numberc: number) => { let count: numbercount = c: numberc; } }; }

在测试文件中使用符文(Using runes inside your test files)

¥Using runes inside your test files

由于 Vitest 以与源文件相同的方式处理你的测试文件,因此只要文件名包含 .svelte,你就可以在测试中使用符文:

¥Since Vitest processes your test files the same way as your source files, you can use runes inside your tests as long as the filename includes .svelte:

multiplier.svelte.test
import { function flushSync(fn?: (() => void) | undefined): void

Synchronously flushes any pending state changes and those that result from it.

flushSync
} from 'svelte';
import { const expect: ExpectStaticexpect, const test: TestAPI

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
} from 'vitest';
import { import multipliermultiplier } from './multiplier.svelte.js'; test<object>(name: string | Function, fn?: TestFunction<object> | undefined, options?: number | TestOptions): void (+2 overloads)

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
('Multiplier', () => {
let let count: numbercount =
function $state<0>(initial: 0): 0 (+1 overload)
namespace $state

Declares reactive state.

Example:

let count = $state(0);

https://svelte.dev/docs/svelte/$state

@paraminitial The initial value
$state
(0);
let let double: anydouble = import multipliermultiplier(() => let count: numbercount, 2); expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)expect(let double: anydouble.value).JestAssertion<any>.toEqual: <number>(expected: number) => voidtoEqual(0); let count: numbercount = 5; expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)expect(let double: anydouble.value).JestAssertion<any>.toEqual: <number>(expected: number) => voidtoEqual(10); });
multiplier.svelte
/**

 * @param {() => number} getCount

 * @param {number} k
 */
export function 
function multiplier(getCount: () => number, k: number): {
    readonly value: number;
}
@paramgetCount
@paramk
multiplier
(getCount: () => number
@paramgetCount
getCount
, k: number
@paramk
k
) {
return { get value: numbervalue() { return getCount: () => number
@paramgetCount
getCount
() * k: number
@paramk
k
;
} }; }
export function 
function multiplier(getCount: () => number, k: number): {
    readonly value: number;
}
multiplier
(getCount: () => numbergetCount: () => number, k: numberk: number) {
return { get value: numbervalue() { return getCount: () => numbergetCount() * k: numberk; } }; }

如果正在测试的代码使用效果,则需要将测试封装在 $effect.root 内:

¥If the code being tested uses effects, you need to wrap the test inside $effect.root:

logger.svelte.test
import { function flushSync(fn?: (() => void) | undefined): void

Synchronously flushes any pending state changes and those that result from it.

flushSync
} from 'svelte';
import { const expect: ExpectStaticexpect, const test: TestAPI

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
} from 'vitest';
import { import loggerlogger } from './logger.svelte.js'; test<object>(name: string | Function, fn?: TestFunction<object> | undefined, options?: number | TestOptions): void (+2 overloads)

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
('Effect', () => {
const const cleanup: () => voidcleanup =
namespace $effect
function $effect(fn: () => void | (() => void)): void

Runs code when a component is mounted to the DOM, and then whenever its dependencies change, i.e. $state or $derived values. The timing of the execution is after the DOM has been updated.

Example:

$effect(() => console.log('The count is now ' + count));

If you return a function from the effect, it will be called right before the effect is run again, or when the component is unmounted.

Does not run during server side rendering.

https://svelte.dev/docs/svelte/$effect

@paramfn The function to execute
$effect
.function $effect.root(fn: () => void | (() => void)): () => void

The $effect.root rune is an advanced feature that creates a non-tracked scope that doesn’t auto-cleanup. This is useful for nested effects that you want to manually control. This rune also allows for creation of effects outside of the component initialisation phase.

Example:

&#x3C;script>
  let count = $state(0);

  const cleanup = $effect.root(() => {
	$effect(() => {
			console.log(count);
		})

	 return () => {
	   console.log('effect root cleanup');
			}
  });
&#x3C;/script>

&#x3C;button onclick={() => cleanup()}>cleanup&#x3C;/button>

https://svelte.dev/docs/svelte/$effect#$effect.root

root
(() => {
let let count: numbercount =
function $state<0>(initial: 0): 0 (+1 overload)
namespace $state

Declares reactive state.

Example:

let count = $state(0);

https://svelte.dev/docs/svelte/$state

@paraminitial The initial value
$state
(0);
// logger uses an $effect to log updates of its input let let log: anylog = import loggerlogger(() => let count: numbercount); // effects normally run after a microtask, // use flushSync to execute all pending effects synchronously function flushSync(fn?: (() => void) | undefined): void

Synchronously flushes any pending state changes and those that result from it.

flushSync
();
expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)expect(let log: anylog.value).JestAssertion<any>.toEqual: <number[]>(expected: number[]) => voidtoEqual([0]); let count: numbercount = 1; function flushSync(fn?: (() => void) | undefined): void

Synchronously flushes any pending state changes and those that result from it.

flushSync
();
expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)expect(let log: anylog.value).JestAssertion<any>.toEqual: <number[]>(expected: number[]) => voidtoEqual([0, 1]); }); const cleanup: () => voidcleanup(); });
logger.svelte
/**

 * @param {() => any} getValue
 */
export function 
function logger(getValue: () => any): {
    readonly value: any[];
}
@paramgetValue
logger
(getValue: () => any
@paramgetValue
getValue
) {
/** @type {any[]} */ let let log: any[]
@type{any[]}
log
=
function $state<never[]>(initial: never[]): never[] (+1 overload)
namespace $state

Declares reactive state.

Example:

let count = $state(0);

https://svelte.dev/docs/svelte/$state

@paraminitial The initial value
$state
([]);
function $effect(fn: () => void | (() => void)): void
namespace $effect

Runs code when a component is mounted to the DOM, and then whenever its dependencies change, i.e. $state or $derived values. The timing of the execution is after the DOM has been updated.

Example:

$effect(() => console.log('The count is now ' + count));

If you return a function from the effect, it will be called right before the effect is run again, or when the component is unmounted.

Does not run during server side rendering.

https://svelte.dev/docs/svelte/$effect

@paramfn The function to execute
$effect
(() => {
let log: any[]
@type{any[]}
log
.Array<any>.push(...items: any[]): number

Appends new elements to the end of an array, and returns the new length of the array.

@paramitems New elements to add to the array.
push
(getValue: () => any
@paramgetValue
getValue
());
}); return { get value: any[]value() { return let log: any[]
@type{any[]}
log
;
} }; }
export function 
function logger(getValue: () => any): {
    readonly value: any[];
}
logger
(getValue: () => anygetValue: () => any) {
let let log: any[]log: any[] =
function $state<never[]>(initial: never[]): never[] (+1 overload)
namespace $state

Declares reactive state.

Example:

let count = $state(0);

https://svelte.dev/docs/svelte/$state

@paraminitial The initial value
$state
([]);
function $effect(fn: () => void | (() => void)): void
namespace $effect

Runs code when a component is mounted to the DOM, and then whenever its dependencies change, i.e. $state or $derived values. The timing of the execution is after the DOM has been updated.

Example:

$effect(() => console.log('The count is now ' + count));

If you return a function from the effect, it will be called right before the effect is run again, or when the component is unmounted.

Does not run during server side rendering.

https://svelte.dev/docs/svelte/$effect

@paramfn The function to execute
$effect
(() => {
let log: any[]log.Array<any>.push(...items: any[]): number

Appends new elements to the end of an array, and returns the new length of the array.

@paramitems New elements to add to the array.
push
(getValue: () => anygetValue());
}); return { get value: any[]value() { return let log: any[]log; } }; }

组件测试(Component testing)

¥Component testing

可以使用 Vitest 单独测试你的组件。

¥It is possible to test your components in isolation using Vitest.

在编写组件测试之前,请考虑你是否真的需要测试组件,或者是否更关注组件内部的逻辑。如果是这样,请考虑提取该逻辑以单独测试它,而无需组件的开销

¥[!NOTE] Before writing component tests, think about whether you actually need to test the component, or if it’s more about the logic inside the component. If so, consider extracting out that logic to test it in isolation, without the overhead of a component

要开始,请安装 jsdom(一个填充 DOM API 的库):

¥To get started, install jsdom (a library that shims DOM APIs):

npm install -D jsdom

然后调整你的 vite.config.js

¥Then adjust your vite.config.js:

vite.config
import { function defineConfig(config: UserConfig): UserConfig (+3 overloads)defineConfig } from 'vitest/config';

export default function defineConfig(config: UserConfig): UserConfig (+3 overloads)defineConfig({
	UserConfig.plugins?: PluginOption[] | undefined

Array of vite plugins to use.

plugins
: [
/* ... */ ], UserConfig.test?: InlineConfig | undefined

Options for Vitest

test
: {
// If you are testing components client-side, you need to setup a DOM environment. // If not all your files should have this environment, you can use a // `// @vitest-environment jsdom` comment at the top of the test files instead. InlineConfig.environment?: VitestEnvironment | undefined

Running environment

Supports ‘node’, ‘jsdom’, ‘happy-dom’, ‘edge-runtime’

If used unsupported string, will try to load the package vitest-environment-${env}

@default'node'
environment
: 'jsdom'
}, // Tell Vitest to use the `browser` entry points in `package.json` files, even though it's running in Node
UserConfig.resolve?: (ResolveOptions & {
    alias?: AliasOptions;
}) | undefined

Configure resolver

resolve
: var process: NodeJS.Processprocess.NodeJS.Process.env: NodeJS.ProcessEnv

The process.env property returns an object containing the user environment. See environ(7).

An example of this object looks like:

{
  TERM: 'xterm-256color',
  SHELL: '/usr/local/bin/bash',
  USER: 'maciej',
  PATH: '~/.bin/:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin',
  PWD: '/Users/maciej',
  EDITOR: 'vim',
  SHLVL: '1',
  HOME: '/Users/maciej',
  LOGNAME: 'maciej',
  _: '/usr/local/bin/node'
}

It is possible to modify this object, but such modifications will not be reflected outside the Node.js process, or (unless explicitly requested) to other Worker threads. In other words, the following example would not work:

node -e 'process.env.foo = "bar"' &#x26;#x26;&#x26;#x26; echo $foo

While the following will:

import { env } from 'node:process';

env.foo = 'bar';
console.log(env.foo);

Assigning a property on process.env will implicitly convert the value to a string. This behavior is deprecated. Future versions of Node.js may throw an error when the value is not a string, number, or boolean.

import { env } from 'node:process';

env.test = null;
console.log(env.test);
// => 'null'
env.test = undefined;
console.log(env.test);
// => 'undefined'

Use delete to delete a property from process.env.

import { env } from 'node:process';

env.TEST = 1;
delete env.TEST;
console.log(env.TEST);
// => undefined

On Windows operating systems, environment variables are case-insensitive.

import { env } from 'node:process';

env.TEST = 1;
console.log(env.test);
// => 1

Unless explicitly specified when creating a Worker instance, each Worker thread has its own copy of process.env, based on its parent thread’s process.env, or whatever was specified as the env option to the Worker constructor. Changes to process.env will not be visible across Worker threads, and only the main thread can make changes that are visible to the operating system or to native add-ons. On Windows, a copy of process.env on a Worker instance operates in a case-sensitive manner unlike the main thread.

@sincev0.1.27
env
.string | undefinedVITEST
? { ResolveOptions.conditions?: string[] | undefinedconditions: ['browser'] } : var undefinedundefined });

之后,你可以创建一个测试文件,在其中导入要测试的组件,以编程方式与其交互并写下对结果的期望:

¥After that, you can create a test file in which you import the component to test, interact with it programmatically and write expectations about the results:

component.test
import { function flushSync(fn?: (() => void) | undefined): void

Synchronously flushes any pending state changes and those that result from it.

flushSync
, function mount<Props extends Record<string, any>, Exports extends Record<string, any>>(component: ComponentType<SvelteComponent<Props>> | Component<Props, Exports, any>, options: MountOptions<Props>): Exports

Mounts a component to the given target and returns the exports and potentially the props (if compiled with accessors: true) of the component. Transitions will play during the initial render unless the intro option is set to false.

mount
,
function unmount(component: Record<string, any>, options?: {
    outro?: boolean;
} | undefined): Promise<void>

Unmounts a component that was previously mounted using mount or hydrate.

Since 5.13.0, if options.outro is true, transitions will play before the component is removed from the DOM.

Returns a Promise that resolves after transitions have completed if options.outro is true, or immediately otherwise (prior to 5.13.0, returns void).

import { mount, unmount } from 'svelte';
import App from './App.svelte';

const app = mount(App, { target: document.body });

// later...
unmount(app, { outro: true });
unmount
} from 'svelte';
import { const expect: ExpectStaticexpect, const test: TestAPI

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
} from 'vitest';
import
type Component = SvelteComponent<Record<string, any>, any, any>
const Component: LegacyComponentType
Component
from './Component.svelte';
test<object>(name: string | Function, fn?: TestFunction<object> | undefined, options?: number | TestOptions): void (+2 overloads)

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
('Component', () => {
// Instantiate the component using Svelte's `mount` API const
const component: {
    $on?(type: string, callback: (e: any) => void): () => void;
    $set?(props: Partial<Record<string, any>>): void;
} & Record<string, any>
component
=
mount<Record<string, any>, {
    $on?(type: string, callback: (e: any) => void): () => void;
    $set?(props: Partial<Record<string, any>>): void;
} & Record<...>>(component: ComponentType<...> | Component<...>, options: MountOptions<...>): {
    ...;
} & Record<...>

Mounts a component to the given target and returns the exports and potentially the props (if compiled with accessors: true) of the component. Transitions will play during the initial render unless the intro option is set to false.

mount
(const Component: LegacyComponentTypeComponent, {
target: Document | Element | ShadowRoot

Target element where the component will be mounted.

target
: var document: Documentdocument.Document.body: HTMLElement

Specifies the beginning and end of the document body.

MDN Reference

body
, // `document` exists because of jsdom
props?: Record<string, any> | undefined

Component properties.

props
: { initial: numberinitial: 0 }
}); expect<string>(actual: string, message?: string): Assertion<string> (+1 overload)expect(var document: Documentdocument.Document.body: HTMLElement

Specifies the beginning and end of the document body.

MDN Reference

body
.InnerHTML.innerHTML: stringinnerHTML).JestAssertion<string>.toBe: <string>(expected: string) => voidtoBe('<button>0</button>');
// Click the button, then flush the changes so you can synchronously write expectations var document: Documentdocument.Document.body: HTMLElement

Specifies the beginning and end of the document body.

MDN Reference

body
.ParentNode.querySelector<"button">(selectors: "button"): HTMLButtonElement | null (+4 overloads)

Returns the first element that is a descendant of node that matches selectors.

MDN Reference

querySelector
('button').HTMLElement.click(): voidclick();
function flushSync(fn?: (() => void) | undefined): void

Synchronously flushes any pending state changes and those that result from it.

flushSync
();
expect<string>(actual: string, message?: string): Assertion<string> (+1 overload)expect(var document: Documentdocument.Document.body: HTMLElement

Specifies the beginning and end of the document body.

MDN Reference

body
.InnerHTML.innerHTML: stringinnerHTML).JestAssertion<string>.toBe: <string>(expected: string) => voidtoBe('<button>1</button>');
// Remove the component from the DOM
function unmount(component: Record<string, any>, options?: {
    outro?: boolean;
} | undefined): Promise<void>

Unmounts a component that was previously mounted using mount or hydrate.

Since 5.13.0, if options.outro is true, transitions will play before the component is removed from the DOM.

Returns a Promise that resolves after transitions have completed if options.outro is true, or immediately otherwise (prior to 5.13.0, returns void).

import { mount, unmount } from 'svelte';
import App from './App.svelte';

const app = mount(App, { target: document.body });

// later...
unmount(app, { outro: true });
unmount
(
const component: {
    $on?(type: string, callback: (e: any) => void): () => void;
    $set?(props: Partial<Record<string, any>>): void;
} & Record<string, any>
component
);
});

虽然这个过程非常简单,但它也是底层的并且有些脆弱,因为组件的精确结构可能会经常变化。像 @testing-library/svelte 这样的工具可以帮助简化你的测试。上面的测试可以像这样重写:

¥While the process is very straightforward, it is also low level and somewhat brittle, as the precise structure of your component may change frequently. Tools like @testing-library/svelte can help streamline your tests. The above test could be rewritten like this:

component.test
import { function render<C extends unknown, Q extends Queries = typeof import("/Users/q/code/nodejscn/svelte/src/node_modules/.pnpm/@testing-library+dom@10.4.0/node_modules/@testing-library/dom/types/queries")>(Component: ComponentType<...>, options?: SvelteComponentOptions<C>, renderOptions?: RenderOptions<Q>): RenderResult<C, Q>

Render a component into the document.

@template{import('./component-types.js').Component} C
@template{import('@testing-library/dom').Queries} [Q=typeof import('@testing-library/dom').queries]
@paramComponent - The component to render.
@paramoptions - Customize how Svelte renders the component.
@paramrenderOptions - Customize how Testing Library sets up the document and binds queries.
@returnsThe rendered component and bound testing functions.
render
, const screen: Screen<typeof import("/Users/q/code/nodejscn/svelte/src/node_modules/.pnpm/@testing-library+dom@10.4.0/node_modules/@testing-library/dom/types/queries")>screen } from '@testing-library/svelte';
import
const userEvent: {
    readonly setup: typeof setupMain;
    readonly clear: typeof clear;
    readonly click: typeof click;
    readonly copy: typeof copy;
    ... 12 more ...;
    readonly tab: typeof tab;
}
userEvent
from '@testing-library/user-event';
import { const expect: ExpectStaticexpect, const test: TestAPI

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
} from 'vitest';
import
type Component = SvelteComponent<Record<string, any>, any, any>
const Component: LegacyComponentType
Component
from './Component.svelte';
test<object>(name: string | Function, fn?: TestFunction<object> | undefined, options?: number | TestOptions): void (+2 overloads)

Defines a test case with a given name and test function. The test function can optionally be configured with test options.

@paramname - The name of the test or a function that will be used as a test name.
@paramoptionsOrFn - Optional. The test options or the test function if no explicit name is provided.
@paramoptionsOrTest - Optional. The test function or options, depending on the previous parameters.
@throwsError If called inside another test function.
@examplets // Define a simple test test('should add two numbers', () => { expect(add(1, 2)).toBe(3); });
@examplets // Define a test with options test('should subtract two numbers', { retry: 3 }, () => { expect(subtract(5, 2)).toBe(3); });
test
('Component', async () => {
const const user: UserEventuser =
const userEvent: {
    readonly setup: typeof setupMain;
    readonly clear: typeof clear;
    readonly click: typeof click;
    readonly copy: typeof copy;
    ... 12 more ...;
    readonly tab: typeof tab;
}
userEvent
.setup: (options?: Options) => UserEvent

Start a “session” with userEvent. All APIs returned by this function share an input device state and a default configuration.

setup
();
render<SvelteComponent<Record<string, any>, any, any>, typeof import("/Users/q/code/nodejscn/svelte/src/node_modules/.pnpm/@testing-library+dom@10.4.0/node_modules/@testing-library/dom/types/queries")>(Component: ComponentType<...>, options?: SvelteComponentOptions<...> | undefined, renderOptions?: RenderOptions<...> | undefined): RenderResult<...>

Render a component into the document.

@template{import('./component-types.js').Component} C
@template{import('@testing-library/dom').Queries} [Q=typeof import('@testing-library/dom').queries]
@paramComponent - The component to render.
@paramoptions - Customize how Svelte renders the component.
@paramrenderOptions - Customize how Testing Library sets up the document and binds queries.
@returnsThe rendered component and bound testing functions.
render
(const Component: LegacyComponentTypeComponent);
const const button: HTMLElementbutton = const screen: Screen<typeof import("/Users/q/code/nodejscn/svelte/src/node_modules/.pnpm/@testing-library+dom@10.4.0/node_modules/@testing-library/dom/types/queries")>screen.getByRole<HTMLElement>(role: ByRoleMatcher, options?: ByRoleOptions | undefined): HTMLElement (+1 overload)getByRole('button'); expect<HTMLElement>(actual: HTMLElement, message?: string): Assertion<HTMLElement> (+1 overload)expect(const button: HTMLElementbutton).toHaveTextContent(0); await const user: UserEventuser.click: (element: Element) => Promise<void>click(const button: HTMLElementbutton); expect<HTMLElement>(actual: HTMLElement, message?: string): Assertion<HTMLElement> (+1 overload)expect(const button: HTMLElementbutton).toHaveTextContent(1); });

在编写涉及双向绑定、上下文或代码片段属性的组件测试时,最好为特定测试创建一个封装器组件并与其交互。@testing-library/svelte 包含一些 示例

¥When writing component tests that involve two-way bindings, context or snippet props, it’s best to create a wrapper component for your specific test and interact with that. @testing-library/svelte contains some examples.

使用 Playwright 进行 E2E 测试(E2E tests using Playwright)

¥E2E tests using Playwright

E2E(’eslint (linting)’ 的缩写)测试允许你通过用户的眼睛测试完整的应用。本节以 Playwright 为例,但你也可以使用其他解决方案,如 CypressNightwatchJS

¥E2E (short for ‘end to end’) tests allow you to test your full application through the eyes of the user. This section uses Playwright as an example, but you can also use other solutions like Cypress or NightwatchJS.

要开始使用 Playwright,请通过 VS Code 扩展 安装它,或使用 npm init playwright 从命令行安装它。当你运行 npx sv create 时,它也是设置 CLI 的一部分。

¥To get started with Playwright, either install it via the VS Code extension, or install it from the command line using npm init playwright. It is also part of the setup CLI when you run npx sv create.

完成此操作后,你应该有一个 tests 文件夹和一个 Playwright 配置。你可能需要调整该配置以告诉 Playwright 在运行测试之前要做什么 - 主要在某个端口启动应用:

¥After you’ve done that, you should have a tests folder and a Playwright config. You may need to adjust that config to tell Playwright what to do before running the tests - mainly starting your application at a certain port:

playwright.config
const 
const config: {
    webServer: {
        command: string;
        port: number;
    };
    testDir: string;
    testMatch: RegExp;
}
config
= {
webServer: {
    command: string;
    port: number;
}
webServer
: {
command: stringcommand: 'npm run build && npm run preview', port: numberport: 4173 }, testDir: stringtestDir: 'tests', testMatch: RegExptestMatch: /(.+\.)?(test|spec)\.[jt]s/ }; export default
const config: {
    webServer: {
        command: string;
        port: number;
    };
    testDir: string;
    testMatch: RegExp;
}
config
;

你现在可以开始编写测试了。这些完全不知道 Svelte 是一个框架,因此你主要与 DOM 交互并编写断言。

¥You can now start writing tests. These are totally unaware of Svelte as a framework, so you mainly interact with the DOM and write assertions.

tests/hello-world.spec
import { import expectexpect, import testtest } from '@playwright/test';

import testtest('home page has expected h1', async ({ page }) => {
	await page: anypage.goto('/');
	await import expectexpect(page: anypage.locator('h1')).toBeVisible();
});
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