title: Why Mocha couldn't find module? Cannot find module 'expect.js'
body: <p>I run <code>mocha test</code> but got error</p>
  
  <pre><code>Error: Cannot find module 'expect.js'
  </code></pre>
  
  <p>My package.json</p>
  
  <pre><code>{
    "name": "new-restexpress",
    "version": "1.0.0",
    "description": "",
    "main": "index.js",
    "directories": {
      "test": "test"
    },
    "scripts": {
      "start": "node index.js",
      "test": "PORT=3007 ./node_modules/.bin/mocha test -R spec"
    },
    "author": "Richard Rublev",
    "license": "ISC",
    "devDependencies": {
      "eslint": "^6.8.0",
      "eslint-config-prettier": "^6.10.1",
      "eslint-plugin-prettier": "^3.1.3",
      "expect": "^25.3.0",
      "mocha": "^7.1.1",
      "prettier": "^2.0.4",
      "standard": "^14.3.3",
      "superagent": "^5.2.2"
    },
    "dependencies": {
      "body-parser": "^1.19.0",
      "express": "^4.17.1",
      "mongodb": "^2.2.36",
      "mongoskin": "^2.1.0",
      "morgan": "^1.10.0"
    }
  }
  </code></pre>
  
  <p>I looked with tree -d</p>
  
  <pre><code>│   ├── expect
  │   │   ├── build
  │   │   │   └── ts3.4
  │   │   ├── build-es5
  │   │   └── node_modules
  │   │       ├── ansi-styles
  │   │       ├── color-convert
  │   │       └── color-name
  </code></pre>
  
  <p>Why is expect not recognized?</p>