create test for createDeferredListener

test/listener.test.js

@@ -0,0 +1,28 @@
+import sinon from "sinon";
+import { createDeferredListener } from "../src/listener";
+
+describe("createDeferredListener", () => {
+  it("queues calls to the listener", async () => {
+    const { setListener, listener } = createDeferredListener();
+    const spy = sinon.spy();
+
+    // Trigger a couple of events
+    listener("message", "sender", "sendResponse");
+    listener("message2", "sender2", "sendResponse2");
+
+    // Listener should receive previous messages
+    setListener(spy);
+
+    // Trigger more events
+    listener("message3", "sender3", "sendResponse3");
+    listener("message4", "sender4", "sendResponse4");
+
+    await Promise.resolve();
+
+    spy.callCount.should.equal(4);
+    spy.getCall(0).args.should.eql(["message", "sender", "sendResponse"]);
+    spy.getCall(1).args.should.eql(["message2", "sender2", "sendResponse2"]);
+    spy.getCall(2).args.should.eql(["message3", "sender3", "sendResponse3"]);
+    spy.getCall(3).args.should.eql(["message4", "sender4", "sendResponse4"]);
+  });
+});