add popper.js

public/vendor/popper.js/packages/test/bin/karma.js

@@ -0,0 +1,14 @@
+#!/usr/bin/env node
+const path = require('path');
+const { Server, config } = require('karma');
+
+const karmaConfig = config.parseConfig(
+  path.resolve(__dirname, '../karma.conf.js')
+);
+
+const server = new Server(karmaConfig, exitCode => {
+  console.log('Karma has exited with ' + exitCode);
+  process.exit(exitCode);
+});
+
+server.start();