reactjs – 错误：看起来你没有加载全局文档就调用了`mount()`

从Enzyme docs开始：

Since enzyme’s mount API requires a DOM,JSDOM is required in order to
use mount if you are not already in a browser environment (ie,a Node
environment).

JSDOM is a JavaScript based headless browser that can be used to
create a realistic testing environment.

For the best experience with enzyme,it is recommended that you load a
document into the global scope before requiring React for the first
time. It is very important that the below script gets run before
React’s code is run.

As a result,a standalone script like the one below is generally a good approach:

/* setup.js */

var jsdom = require('jsdom').jsdom;

var exposedProperties = ['window','navigator','document'];

global.document = jsdom('');
global.window = document.defaultView;
Object.keys(document.defaultView).forEach((property) => {
  if (typeof global[property] === 'undefined') {
    exposedProperties.push(property);
    global[property] = document.defaultView[property];
  }
});

global.navigator = {
  userAgent: 'node.js'
};

阅读Enzyme documentation – JSDOM以获取更多信息