Jest 平台工具

你可以自由选择Jest的特定功能，并独立使用这些包。 Here’s a list of the available packages:

jest-changed-files

用于识别 git/hg 存储库中已修改文件的工具。导出两个函数：

getChangedFilesForRoots 返回一个resolved状态的Promise，此Promise包含修改文件和仓库信息。
findRepos 返回一个resolved状态的Promise，此Promise包含指定路径的一组仓库数据。

例子

const {getChangedFilesForRoots} = require('jest-changed-files');
// 打印出当前目录最后修改过的一组文件
getChangedFilesForRoots(['./'], {
  lastCommit: true,
}).then(result => console.log(result.changedFiles));

You can read more about jest-changed-files in the readme file.

jest-diff

数据更改的可视化工具。输出一个函数，两个任何类型的值输入该函数后，返回一个“较易读”的字符串来展现其区别。

例子

const {diff} = require('jest-diff');
const a = {a: {b: {c: 5}}};
const b = {a: {b: {c: 6}}};
const result = diff(a, b);
// print diff
console.log(result);

jest-docblock

Tool for extracting and parsing the comments at the top of a JavaScript file. Exports various functions to manipulate the data inside the comment block. Exports various functions to manipulate the data inside the comment block.

例子

const {parseWithComments} = require('jest-docblock');
const code = `
/**
 * This is a sample
 *
 * @flow
 */
 console.log('Hello World!');
`;
const parsed = parseWithComments(code);
// prints an object with two attributes: comments and pragmas.
console.log(parsed);
console.log(parsed);

You can read more about jest-docblock in the readme file.

jest-get-type

Module that identifies the primitive type of any JavaScript value. Module that identifies the primitive type of any JavaScript value. Exports a function that returns a string with the type of the value passed as argument.

例子

const {getType} = require('jest-get-type');
const array = [1, 2, 3];
const nullValue = null;
const undefinedValue = undefined;
// prints 'array'
console.log(getType(array));
// prints 'null'
console.log(getType(nullValue));
// prints 'undefined'
console.log(getType(undefinedValue));

jest-validate

用于验证用户提交的配置的工具。 Exports a function that takes two arguments: the user’s configuration and an object containing an example configuration and other options. The return value is an object with two attributes: The return value is an object with two attributes:

hasDeprecationWarnings, a boolean indicating whether the submitted configuration has deprecation warnings,
isValid, 一个布尔值, 指示配置是否正确。

例子

const {validate} = require('jest-validate');
const configByUser = {
  transform: '<rootDir>/node_modules/my-custom-transform',
};
const result = validate(configByUser, {
  comment: '  Documentation: http://custom-docs.com',
  exampleConfig: {transform: '<rootDir>/node_modules/babel-jest'},
});
console.log(result);

You can read more about jest-validate in the readme file.

jest-worker

用于任务并行化的模块。 Exports a class JestWorker that takes the path of Node.js module and lets you call the module’s exported methods as if they were class methods, returning a promise that resolves when the specified method finishes its execution in a forked process.

例子

heavy-task.js

module.exports = {
  myHeavyTask: args => {
    // long running CPU intensive task.
  },
};

main.js

async function main() {
  const worker = new Worker(require.resolve('./heavy-task.js'));
  // run 2 tasks in parallel with different arguments
  const results = await Promise.all([
    worker.myHeavyTask({foo: 'bar'}),
    worker.myHeavyTask({bar: 'foo'}),
  ]);
  console.log(results);
}
main();

You can read more about jest-worker in the readme file.

pretty-format

Exports a function that converts any JavaScript value into a human-readable string. Supports all built-in JavaScript types out of the box and allows extension for application-specific types via user-defined plugins. Supports all built-in JavaScript types out of the box and allows extension for application-specific types via user-defined plugins.

例子

const {format: prettyFormat} = require('pretty-format');
const val = {object: {}};
val.circularReference = val;
val[Symbol('foo')] = 'foo';
val.map = new Map([['prop', 'value']]);
val.array = [-0, Infinity, NaN];
console.log(prettyFormat(val));

You can read more about pretty-format in the readme file.