Failed to write coverage reports:
        ERROR: Error: EEXIST: file already exists, mkdir 'xxx\tests\coverage\vue-cli-3\dist\js'
        STACK: Error: EEXIST: file already exists, mkdir 'xxx\tests\coverage\vue-cli-3\dist\js'
    at Object.mkdirSync (fs.js:738:3)
    at sync (xxx\node_modules\mkdirp\index.js:71:13)
    at sync (xxx\node_modules\mkdirp\index.js:77:24)
    at sync (xxx\node_modules\mkdirp\index.js:78:17)
    at sync (xxx\node_modules\mkdirp\index.js:78:17)
    at sync (xxx\node_modules\mkdirp\index.js:78:17)
    at sync (xxx\node_modules\mkdirp\index.js:78:17)
    at sync (xxx\node_modules\mkdirp\index.js:78:17)
    at sync (xxx\node_modules\mkdirp\index.js:78:17)
    at sync (xxx\node_modules\mkdirp\index.js:78:17)

百度、谷歌没有无果。后来修改了 jest.config.js 里的 collectCoverageFrom 匹配规格解决问题。

// jest.config.js
model.export={
  // ...
    collectCoverageFrom: [
    　　'**/*.{js,vue}',
    　　'!**/node_modules/**'
  // ...      
// jest.config.js
model.export={
  // ...
    collectCoverageFrom: [
    　  'src/**/*.{js,vue}',
        '!src/main.js',
        '!src/router/index.js',
        '!**/node_modules/**'
  // ...