some frontend unit tests

test/frontend/index.js

@@ -0,0 +1,16 @@
+const fs = require('fs');
+const path = require('path');
+
+function kv(f) {
+  return `require('./tests/${f}')`;
+}
+
+module.exports = function() {
+  const files = fs.readdirSync(path.join(__dirname, 'tests'));
+  const code = files.map(kv).join(';\n');
+  return {
+    code,
+    dependencies: files.map(f => require.resolve('./tests/' + f)),
+    cacheable: false
+  };
+};