Webpack is using this, which should explicitly ignore the test folder.

      {
        test: /\.ts$/,
        use: [{
          loader: 'ts-loader'
          //loader: 'awesome-typescript-loader'

        }]
        ,
        exclude: '/**/*.test.ts'
      }

but it tried to compile my tests (which results in a failing as tests run in node and the webpack build doesn't expect assert to be available in a browser build )

ERROR in /Users/nikos/WebstormProjects/solar-popup/src/tests/SolarPopup.test.ts
(2,20): error TS2307: Cannot find module 'assert'.

The browser webpack build targets es2015:

{
  "compilerOptions": {
    "target": "es2015",
    "declaration": true
  },
  "exclude": [
    "node_modules",
    "demo"
  ]
}