title: Error TS2688 Build:Cannot find type definition file for 'mocha' after TypeScript update
body: <p>I, am keep getting the <strong>error: Cannot find type definition file for 'mocha'</strong> when I update the TypeScript to latest version.</p>
  
  <p><strong>tsconfig.json</strong></p>
  
  <pre><code>    {
    "compilerOptions": {
      "emitDecoratorMetadata": true,
      "experimentalDecorators": true,
      "lib": [ "es2015", "dom" ],
      "module": "commonjs",
      "moduleResolution": "node",
      "noImplicitAny": true,
      "sourceMap": true,
      "suppressImplicitAnyIndexErrors": true,
      "target": "es5",
      "rootDir": "app",
      "outDir": "wwwroot/app"
    },
    "exclude": [
      "node_modules",
      "wwwroot/node_modules",
      "typings"
  
    ]
  }
  </code></pre>
  
  <p>I, have not change any things. It was working perfectly earlier just I update the TypeScript version from 2.2.2 to 2.5 and keep getting error. I, am using Angular 4</p>
  
  <p><strong>Package.json</strong></p>
  
  <pre><code>    {
    "version": "1.0.0",
    "name": "asp.net",
    "private": true,
    "dependencies": {
      "@angular/common": "^4.0.0",
      "@angular/compiler": "^4.0.0",
      "@angular/compiler-cli": "^4.0.0",
      "@angular/core": "^4.0.0",
      "@angular/forms": "^4.0.0",
      "@angular/http": "^4.0.0",
      "@angular/platform-browser": "^4.0.0",
      "@angular/platform-browser-dynamic": "^4.0.0",
      "@angular/platform-server": "^4.0.0",
      "@angular/router": "^4.0.0",
      "@angular/upgrade": "2.0.0",
      "angular2-in-memory-web-api": "0.0.20",
      "core-js": "^2.4.1",
      "reflect-metadata": "^0.1.9",
      "rxjs": "5.0.2",
      "systemjs": "0.19.27",
      "typescript": "^2.4.1",
      "zone.js": "0.7.6"
    },
    "devDependencies": {}
  }
  </code></pre>