测试
测试可以帮助您编写和维护代码,并防止出现回归问题。测试框架可以帮助您实现这一点,允许您描述关于代码行为的断言或期望。Svelte 对使用哪个测试框架没有偏好——您可以使用 Vitest、Jasmine、Cypress 和 Playwright 等解决方案编写单元测试、集成测试和端到端测试。
使用 Vitest 进行单元和集成测试
单元测试允许您测试代码的小而隔离的部分。集成测试允许您测试应用程序的部分,以查看它们是否协同工作。如果您使用 Vite(包括通过 SvelteKit),我们建议使用 Vitest。
要开始使用,请安装 Vitest
npm install -D vitest
然后调整您的 vite.config.js
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.Process
process.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.
env.string | undefined
VITEST
? {
ResolveOptions.conditions?: string[] | undefined
conditions: ['browser']
}
: var undefined
undefined
});
如果加载所有软件包的浏览器版本不可取,例如,您还测试后端库,您可能需要采用别名配置
您现在可以为 .js/.ts
文件中的代码编写单元测试
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: ExpectStatic
expect, const test: TestAPI
Defines a test case with a given name and test function. The test function can optionally be configured with test options.
test } from 'vitest';
import { import multiplier
multiplier } from './multiplier.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.
test('Multiplier', () => {
let let double: any
double = import multiplier
multiplier(0, 2);
expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)
expect(let double: any
double.value).JestAssertion<any>.toEqual: <number>(expected: number) => void
toEqual(0);
let double: any
double.set(5);
expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)
expect(let double: any
double.value).JestAssertion<any>.toEqual: <number>(expected: number) => void
toEqual(10);
});
在测试文件中使用符文
可以在测试文件中使用符文。首先确保您的打包器知道在运行测试之前通过 Svelte 编译器路由文件,方法是在文件名中添加 .svelte
(例如 multiplier.svelte.test.js
)。之后,您可以在测试中使用符文。
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: ExpectStatic
expect, const test: TestAPI
Defines a test case with a given name and test function. The test function can optionally be configured with test options.
test } from 'vitest';
import { import multiplier
multiplier } 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.
test('Multiplier', () => {
let let count: number
count = function $state<0>(initial: 0): 0 (+1 overload)
namespace $state
$state(0);
let let double: any
double = import multiplier
multiplier(() => let count: number
count, 2);
expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)
expect(let double: any
double.value).JestAssertion<any>.toEqual: <number>(expected: number) => void
toEqual(0);
let count: number
count = 5;
expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)
expect(let double: any
double.value).JestAssertion<any>.toEqual: <number>(expected: number) => void
toEqual(10);
});
如果正在测试的代码使用效果,则需要将测试包装在 $effect.root
中
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: ExpectStatic
expect, const test: TestAPI
Defines a test case with a given name and test function. The test function can optionally be configured with test options.
test } from 'vitest';
import { import logger
logger } 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.
test('Effect', () => {
const const cleanup: () => void
cleanup = 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.
$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:
<script>
let count = $state(0);
const cleanup = $effect.root(() => {
$effect(() => {
console.log(count);
})
return () => {
console.log('effect root cleanup');
}
});
</script>
<button onclick={() => cleanup()}>cleanup</button>
root(() => {
let let count: number
count = function $state<0>(initial: 0): 0 (+1 overload)
namespace $state
$state(0);
// logger uses an $effect to log updates of its input
let let log: any
log = import logger
logger(() => let count: number
count);
// effects normally run after a microtask,
// use flushSync to execute all pending effects synchronously
function flushSync(fn?: (() => void) | undefined): void
Synchronously flushes any pending state changes and those that result from it.
flushSync();
expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)
expect(let log: any
log.value).JestAssertion<any>.toEqual: <number[]>(expected: number[]) => void
toEqual([0]);
let count: number
count = 1;
function flushSync(fn?: (() => void) | undefined): void
Synchronously flushes any pending state changes and those that result from it.
flushSync();
expect<any>(actual: any, message?: string): Assertion<any> (+1 overload)
expect(let log: any
log.value).JestAssertion<any>.toEqual: <number[]>(expected: number[]) => void
toEqual([0, 1]);
});
const cleanup: () => void
cleanup();
});
组件测试
可以使用 Vitest 隔离测试您的组件。
在编写组件测试之前,请考虑您是否真的需要测试组件,或者它更多的是关于组件内部的逻辑。如果是这样,请考虑提取该逻辑以独立测试它,而无需组件的开销
要开始使用,请安装 jsdom(一个模拟 DOM API 的库)
npm install -D jsdom
然后调整您的 vite.config.js
import { function defineConfig(config: UserConfig): UserConfig (+3 overloads)
defineConfig } from 'vitest/config';
export default function defineConfig(config: UserConfig): UserConfig (+3 overloads)
defineConfig({
UserConfig.plugins?: PluginOption[] | undefined
Array of vite plugins to use.
plugins: [
/* ... */
],
UserConfig.test?: InlineConfig | undefined
Options for Vitest
test: {
// If you are testing components client-side, you need to setup a DOM environment.
// If not all your files should have this environment, you can use a
// `// @vitest-environment jsdom` comment at the top of the test files instead.
InlineConfig.environment?: VitestEnvironment | undefined
Running environment
Supports ‘node’, ‘jsdom’, ‘happy-dom’, ‘edge-runtime’
If used unsupported string, will try to load the package vitest-environment-${env}
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.Process
process.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; 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.
env.string | undefined
VITEST
? {
ResolveOptions.conditions?: string[] | undefined
conditions: ['browser']
}
: var undefined
undefined
});
之后,您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编写关于结果的期望
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>): void
Unmounts a component that was previously mounted using mount
or hydrate
.
unmount } from 'svelte';
import { const expect: ExpectStatic
expect, const test: TestAPI
Defines a test case with a given name and test function. The test function can optionally be configured with test options.
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.
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: LegacyComponentType
Component, {
target: Document | Element | ShadowRoot
Target element where the component will be mounted.
target: var document: Document
document.Document.body: HTMLElement
Specifies the beginning and end of the document body.
body, // `document` exists because of jsdom
props?: Record<string, any> | undefined
Component properties.
props: { initial: number
initial: 0 }
});
expect<string>(actual: string, message?: string): Assertion<string> (+1 overload)
expect(var document: Document
document.Document.body: HTMLElement
Specifies the beginning and end of the document body.
body.InnerHTML.innerHTML: string
innerHTML).JestAssertion<string>.toBe: <string>(expected: string) => void
toBe('<button>0</button>');
// Click the button, then flush the changes so you can synchronously write expectations
var document: Document
document.Document.body: HTMLElement
Specifies the beginning and end of the document body.
body.ParentNode.querySelector<"button">(selectors: "button"): HTMLButtonElement | null (+4 overloads)
Returns the first element that is a descendant of node that matches selectors.
querySelector('button').HTMLElement.click(): void
click();
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: Document
document.Document.body: HTMLElement
Specifies the beginning and end of the document body.
body.InnerHTML.innerHTML: string
innerHTML).JestAssertion<string>.toBe: <string>(expected: string) => void
toBe('<button>1</button>');
// Remove the component from the DOM
function unmount(component: Record<string, any>): void
Unmounts a component that was previously mounted using mount
or hydrate
.
unmount(const component: {
$on?(type: string, callback: (e: any) => void): () => void;
$set?(props: Partial<Record<string, any>>): void;
} & Record<string, any>
component);
});
虽然该过程非常简单,但也属于低级且有些脆弱,因为组件的精确结构可能会频繁更改。像 @testing-library/svelte 这样的工具可以帮助简化您的测试。上面的测试可以改写如下
import { function render<C extends unknown, Q extends Queries = typeof import("/vercel/path0/node_modules/.pnpm/@[email protected]/node_modules/@testing-library/dom/types/queries")>(Component: ComponentType<...>, options?: SvelteComponentOptions<C>, renderOptions?: RenderOptions<Q>): RenderResult<C, Q>
Render a component into the document.
render, const screen: Screen<typeof import("/vercel/path0/node_modules/.pnpm/@[email protected]/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: ExpectStatic
expect, const test: TestAPI
Defines a test case with a given name and test function. The test function can optionally be configured with test options.
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.
test('Component', async () => {
const const user: UserEvent
user = 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("/vercel/path0/node_modules/.pnpm/@[email protected]/node_modules/@testing-library/dom/types/queries")>(Component: ComponentType<...>, options?: SvelteComponentOptions<...> | undefined, renderOptions?: RenderOptions<...> | undefined): RenderResult<...>
Render a component into the document.
render(const Component: LegacyComponentType
Component);
const const button: HTMLElement
button = const screen: Screen<typeof import("/vercel/path0/node_modules/.pnpm/@[email protected]/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: HTMLElement
button).toHaveTextContent(0);
await const user: UserEvent
user.click: (element: Element) => Promise<void>
click(const button: HTMLElement
button);
expect<HTMLElement>(actual: HTMLElement, message?: string): Assertion<HTMLElement> (+1 overload)
expect(const button: HTMLElement
button).toHaveTextContent(1);
});
在编写涉及双向绑定、上下文或代码片段 prop 的组件测试时,最好为您的特定测试创建一个包装器组件并与其交互。@testing-library/svelte
包含一些 示例。
使用 Playwright 进行端到端测试
端到端 (E2E) 测试允许您通过用户的视角测试整个应用程序。本节使用 Playwright 作为示例,但您也可以使用其他解决方案,如 Cypress 或 NightwatchJS。
要开始使用 Playwright,可以通过 VS Code 扩展 安装它,或使用 npm init playwright
从命令行安装它。当您运行 npx sv create
时,它也是设置 CLI 的一部分。
完成后,您应该有一个 tests
文件夹和一个 Playwright 配置文件。您可能需要调整该配置以告诉 Playwright 在运行测试之前该做什么——主要是以特定端口启动您的应用程序
const const config: {
webServer: {
command: string;
port: number;
};
testDir: string;
testMatch: RegExp;
}
config = {
webServer: {
command: string;
port: number;
}
webServer: {
command: string
command: 'npm run build && npm run preview',
port: number
port: 4173
},
testDir: string
testDir: 'tests',
testMatch: RegExp
testMatch: /(.+\.)?(test|spec)\.[jt]s/
};
export default const config: {
webServer: {
command: string;
port: number;
};
testDir: string;
testMatch: RegExp;
}
config;
您现在可以开始编写测试了。这些测试完全不知道 Svelte 作为框架,因此您主要与 DOM 交互并编写断言。
import { import expect
expect, import test
test } from '@playwright/test';
import test
test('home page has expected h1', async ({ page }) => {
await page: any
page.goto('/');
await import expect
expect(page: any
page.locator('h1')).toBeVisible();
});