Add test for SubscribingEventEmitter

__tests__/core/SubscribingEventEmitter.test.ts

@@ -0,0 +1,42 @@
+import { SubscribingEventEmitter } from "../../src/utils/SubscribingEventEmitter";
+
+class Worker extends SubscribingEventEmitter {}
+
+class Subscriber {
+  /**
+   * counter for invocations
+   */
+  public events = {
+    function: 0,
+  };
+
+  getSubscribedEvents() {
+    return {
+      function: () => this.events["function"]++,
+    };
+  }
+}
+
+describe("utils", () => {
+  describe("SubscribingEventEmitter", () => {
+    test("register/unregister listeners", async () => {
+      const worker = new Worker();
+      expect(worker.listenerCount("function")).toBe(0);
+
+      worker.addSubscriber(new Subscriber());
+      expect(worker.listenerCount("function")).toBe(1);
+
+      worker.removeAllListeners();
+      expect(worker.listenerCount("function")).toBe(0);
+    });
+
+    test("listerner is called", async () => {
+      const worker = new Worker();
+      const subscriber = new Subscriber();
+      worker.addSubscriber(subscriber);
+      worker.emit("function");
+
+      expect(subscriber.events["function"]).toBe(1);
+    });
+  });
+});