如何使用Jest测试文件下载? [英] How to use Jest to test file download?

问题描述

我有一些如下代码:

/* global document */
/* global window */
/* global Blob */

import FileSaver from 'file-saver';

export const createDownloadFromBlob = (blob, filename, extension) => {
  FileSaver.saveAs(blob, `${filename}.${extension}`);
};

export const createDownload = (content, filename, extension) => {
  createDownloadFromBlob(new Blob([content], { type: 'application/octet-stream' }), filename, extension);
};

我想用Jest对这两种方法进行单元测试，但是我不知道从哪里开始.任何帮助将不胜感激.

I want to use Jest to unit-test these two methods, but I don't know where to start. Any help would be appreciated.

推荐答案

我会用间谍来模拟FileSaver:

import FileSaver from 'file-saver';
jest.mock('file-saver', ()=>({saveAs: jest.fn()}))

由于您无法比较Blob，因此我也会对此进行嘲笑:

As you cant compare Blobs I would mock this as well:

global.Blob = function (content, options){return  ({content, options})}

现在您可以运行测试并使用期望值

now you can run your test and use expect like this

createDownload('content', 'filename', 'extension')
expect(FileSaver.saveAs).toHaveBeenCalledWith(
  {content:'content', options: { type: 'application/octet-stream' }}, 
  'filename.extension'
)

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