title: tsconfig.json for project with `src` and `tests`
body: <p>I've got a (desired) structure like this:</p>
  
  <pre><code>- tsconfig.json
  - src
      - app.ts
  - tests
      - appTest.ts
      - appTest.js
  - dist
      - app.js
  </code></pre>
  
  <p>If there was no <code>tests</code> folder, a tsconfig.json like this would work fine:</p>
  
  <pre><code>{
      "compilerOptions": {
          "outDir":"dist"
      },
      "include" :[
          "src/**/*.ts"
      ]
  }
  </code></pre>
  
  <p>However, if I add <code>tests/**/*.ts</code> to the <code>include</code> element, it also compiles my test files into <code>dist</code> and changes its folder structure (understandably, but undesirably).</p>
  
  <p>Can I tell TypeScript compiler to include test files in the project to support things like refactoring but omit them from output to <code>dist</code>? Specifically, I'd like the <code>.js</code> to be compiled in the <code>tests</code> directory as suggested in the structure above.</p>