use jest for CI

test/lib/util.spec.js

@@ -0,0 +1,20 @@
+const util = require('../../lib/util');
+
+describe('utils', () => {
+  it('getFreePort', async () => {
+    const count = 100;
+    const tasks = [];
+    for (let i = 1; i <= count; i++) {
+      tasks.push(util.getFreePort());
+    }
+    await Promise.all(tasks)
+      .then((results) => {
+        // ensure ports are unique
+        const portMap = {};
+        results.map((portNumber) => {
+          portMap[portNumber] = true;
+        });
+        expect(Object.keys(portMap).length).toEqual(count);
+      });
+  });
+});