Add basic tests for watchdog using jest

assets/static/watchdog.test.js

@@ -0,0 +1,9 @@
+const watchdog = require("./watchdog");
+
+test("watchdog init", () => {
+    watchdog.init();
+});
+
+test("watchdog getTs without pong", () => {
+    expect(watchdog.getTs).toBe(undefined);
+});