title: TypeError [ERR_UNKNOWN_FILE_EXTENSION]: Unknown file extension ".ts" on Visual Studio Code
body: <p>I've been working on unit-testing some code, and out of seemingly nowhere, I got an error about unknown file extensions (before, I got errors about how some type wasn't recognized).</p>
  <p>Here is my package.json:</p>
  <pre><code>{
    &quot;name&quot;: &quot;cgt-core-engine-mv&quot;,
    &quot;description&quot;: &quot;API container for other CGT plugins&quot;,
    &quot;version&quot;: &quot;1.01.03&quot;,
    &quot;author&quot;: &quot;CG-Tespy&quot;,
    &quot;repository&quot;: {
      &quot;type&quot;: &quot;git&quot;,
      &quot;url&quot;: &quot;https://github.com/CG-Tespy/CGT_CoreEngine_MV&quot;
    },
    &quot;scripts&quot;: {
      &quot;build&quot;: &quot;tsc &amp; (rollup -c)&quot;,
      &quot;test&quot;: &quot;mocha -r ts-node/register Test/**/*.ts&quot;
    },
    &quot;dependencies&quot;: {},
    &quot;devDependencies&quot;: {
      &quot;@types/chai&quot;: &quot;^4.2.12&quot;,
      &quot;@types/mocha&quot;: &quot;^8.0.0&quot;,
      &quot;@types/sinon&quot;: &quot;^9.0.4&quot;,
      &quot;chai&quot;: &quot;^4.2.0&quot;,
      &quot;mocha&quot;: &quot;^8.0.1&quot;,
      &quot;rollup&quot;: &quot;^2.00.1&quot;,
      &quot;rollup-plugin-node-resolve&quot;: &quot;^5.2.0&quot;,
      &quot;rollup-pluginutils&quot;: &quot;^2.8.2&quot;,
      &quot;sinon&quot;: &quot;^9.0.2&quot;,
      &quot;ts-node&quot;: &quot;^8.10.2&quot;,
      &quot;typescript&quot;: &quot;^3.9.6&quot;
    },
    &quot;type&quot;: &quot;module&quot;
  }
  </code></pre>
  <p>Here is my tsconfig.json:</p>
  <pre><code>{
      &quot;compilerOptions&quot;: {
        &quot;target&quot;: &quot;es5&quot;,
        &quot;module&quot;: &quot;CommonJS&quot;,
        &quot;esModuleInterop&quot;: true,
  
        &quot;sourceMap&quot;: false,
        &quot;downlevelIteration&quot;: true,
      },
      &quot;include&quot;: [&quot;_MainSource/**/*&quot;, &quot;Tests/**/*&quot;, &quot;@typeDefs/**/*&quot;],
  }
  </code></pre>
  <p>I really have no idea where this came from. I have a separate project where I was able to unit-test things just fine, and it didn't give me any errors. The package.json for it:</p>
  <pre><code>{
    &quot;name&quot;: &quot;unittesting&quot;,
    &quot;version&quot;: &quot;1.0.0&quot;,
    &quot;description&quot;: &quot;For practicing unit-testing&quot;,
    &quot;main&quot;: &quot;main.js&quot;,
    &quot;scripts&quot;: {
      &quot;test&quot;: &quot;mocha -r ts-node/register test/**/*.ts&quot;
      
    },
    &quot;author&quot;: &quot;&quot;,
    &quot;license&quot;: &quot;ISC&quot;,
    &quot;devDependencies&quot;: {
      &quot;@types/chai&quot;: &quot;^4.2.11&quot;,
      &quot;@types/mocha&quot;: &quot;^8.0.0&quot;,
      &quot;chai&quot;: &quot;^4.2.0&quot;,
      &quot;mocha&quot;: &quot;^8.0.1&quot;,
      &quot;ts-node&quot;: &quot;^8.10.2&quot;,
      &quot;typescript&quot;: &quot;^3.9.7&quot;
    },
    &quot;type&quot;: &quot;module&quot;
  }
  </code></pre>
  <p>Its tsconfig:</p>
  <pre><code>{
    &quot;compilerOptions&quot;: {
      /* Basic Options */
  
      &quot;target&quot;: &quot;es5&quot;,                          /* Specify ECMAScript target version: 'ES3' (default), 'ES5', 'ES2015', 'ES2016', 'ES2017', 'ES2018', 'ES2019', 'ES2020', or 'ESNEXT'. */
      &quot;module&quot;: &quot;CommonJS&quot;,                     /* Specify module code generation: 'none', 'commonjs', 'amd', 'system', 'umd', 'es2015', 'es2020', or 'ESNext'. */
      
      &quot;esModuleInterop&quot;: true,
      
    },
    &quot;include&quot;: [&quot;src/**/*&quot;, &quot;tests/**/*&quot;],
  }
  </code></pre>
  <p>What could be causing this issue? I've tried the suggestions <a href="https://stackoverflow.com/questions/62096269/cant-run-my-node-js-typescript-project-typeerror-err-unknown-file-extension">here</a>, but it didn't work (even after looking at the Github issue linked).</p>