使用 Jest 异步设置环境 [英] Async setup of environment with Jest

问题描述

在 Jest 中运行 e2e 测试之前，我需要从服务器获取身份验证令牌.

Before running e2e tests in Jest I need to get an authentication token from the server.

是否可以全局执行此操作并以某种方式将其设置为每个测试的全局环境/上下文?

Is it possible to do this globally one and set it somehow to the global environment / context for each test ?

我尝试使用 globalSetup 配置选项:

I tried it with globalSetup config option:

const auth = require('./src/auth')
const ctx = require('./src/context')

module.exports = () => {
    return new Promise(res => {
        auth.getToken()
            .then(token => {
                ctx.init({token})
                global.token = token
                res()
            })

    })
}

context.js

let _token

const init = ({token}) => {
    _token = token
}

const getToken = () => {
    return _token
}

module.exports = {
    init,
    getToken

}

但是 global.token 和 ctx.getToken() 都返回 undefined.

But both global.token nor ctx.getToken() return undefined.

我需要使用辅助脚本并将令牌作为 env var 传递，然后将其设置为 global.

I need to use helper script and to pass token as env var which is then set as global.

  "scripts": {
    "test": "TOKEN=$(node src/get-token.js) jest"
  },

有没有更好的方法(不涉及shell)?

Is there a better approach (which does not involve shell) ?

推荐答案

有一个 CLI/config 选项叫做:setupFiles，它会在执行测试代码本身之前立即运行.

There's a CLI/config option called: setupFiles, it runs immediately before executing the test code itself.

"jest": {
  "globals": {
    "__DEV__": true,
    ...
  },
  "setupFiles": [
    "./setup.js"
  ]
}

setup.js 可能类似于:

(async function() {
    // const { authToken } = await fetchAuthTokens()
    global.authToken = '123'
})()

然后您可以直接在每个测试套件(文件)中访问 authToken，例如 beforeAll(_ => console.log(authToken))//123.

And then you can access authToken directly in each test suites (files) like beforeAll(_ => console.log(authToken)) // 123.

但是，如果您想要一个全局设置，它可以在每个 worker(cpu 核心)而不是每个测试文件中运行(默认情况下推荐，因为测试套件是沙盒的).基于当前的 jest API 约束，您可以选择通过 testEnvironment 选项.然后你需要实现一个自定义类，扩展jsdom/node 环境暴露setup/runScript/拆解 api.

However, if you want a global setup that runs per worker(cpu core) instead of per test file (recommended by default since test suites are sandboxed). Based on current jest API constraints, you may choose to customize your test's runtime environment through the testEnvironment option. Then you need to implement a custom class that extends jsdom/node environment exposes setup/runScript/teardown api.

示例:

customEnvironment.js

customEnvironment.js

// my-custom-environment
const NodeEnvironment = require('jest-environment-node');

class CustomEnvironment extends NodeEnvironment {
  constructor(config) {
    super(config);
  }

  async setup() {
    await super.setup();
    const token = await someSetupTasks();
    this.global.authToken = token;
  }

  async teardown() {
    await super.teardown();
    await someTeardownTasks();
  }

  runScript(script) {
    return super.runScript(script);
  }
}

my-test.js

let authToken;

beforeAll(() => {
  authToken = global.authToken;
});

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