test/runner.html

<!DOCTYPE html>
<html>
    <head>
        <title>Sample Test Runner</title>
        <meta charset="utf-8" />
        <link rel="stylesheet" href="../node_modules/mocha/mocha.css" />
        <script src="/node_modules/source-map-support/browser-source-map-support.js"></script>
        <script src="/node_modules/mocha/mocha.js"></script>
        <script src="/node_modules/chai/chai.js"></script>
        <script>
            /* global mocha, sourceMapSupport */
            sourceMapSupport.install();
            mocha.setup('bdd');
        </script>

        <!-- add your components under test here -->
        <script type="module" src="/components/page-banner.js"></script>
        <!-- add you test files here -->
        <script type="module" src="/unit/index.spec.js"></script>
    </head>

    <body>
        <!-- add your test fixtures here -->
        <template id="first">
            <page-banner message="Hello World!"></page-banner>
        </template>

        <div id="mocha"></div>
        <div id="stage"></div>
    </body>
</html>