开玩笑报告首次运行时覆盖率值接近零

Question

我有一个正在用Jest进行单元测试的Vue应用程序。在Linux上，假设我删除了/coverage文件夹，以覆盖率运行Jest会产生接近零的覆盖率值：

=============================== Coverage summary ===============================
Statements   : 100% ( 15/15 )
Branches     : 100% ( 0/0 )
Functions    : 100% ( 0/0 )
Lines        : 100% ( 15/15 )
================================================================================

当我第二次运行Jest时，我得到了真实的结果：

=============================== Coverage summary ===============================
Statements   : 3.6% ( 890/24731 )
Branches     : 0.96% ( 169/17656 )
Functions    : 1.59% ( 125/7858 )
Lines        : 5.6% ( 875/15638 )
================================================================================

为什么会这样，我该如何解决？

我的Jest配置来自package.json：

"jest": {
    "rootDir": "../",
    "moduleFileExtensions": [
      "js",
      "vue"
    ],
    "transform": {
      "^.+\\.vue$": "<rootDir>/tests/node_modules/jest-vue-preprocessor",
      "^.+\\.js$": "<rootDir>/tests/node_modules/babel-jest"
    },
    "moduleNameMapper": {
      "^~/(.*)$": "<rootDir>/$1"
    },
    "collectCoverage": true,
    "collectCoverageFrom": [
      "**/*.{js,vue}",
      "!**/node_modules/**",
      "!**router.js"
    ],
    "coverageReporters": [
      "html",
      "text-summary"
    ],
    "coverageDirectory": "coverage",
    "notify": true,
    "setupTestFrameworkScriptFile": "<rootDir>/tests/setup.js"
}