automaker/apps/server/tests/unit/lib/events.test.ts

import { describe, it, expect, vi } from "vitest";
import { createEventEmitter, type EventType } from "@/lib/events.js";

describe("events.ts", () => {
  describe("createEventEmitter", () => {
    it("should emit events to single subscriber", () => {
      const emitter = createEventEmitter();
      const callback = vi.fn();

      emitter.subscribe(callback);
      emitter.emit("agent:stream", { message: "test" });

      expect(callback).toHaveBeenCalledOnce();
      expect(callback).toHaveBeenCalledWith("agent:stream", { message: "test" });
    });

    it("should emit events to multiple subscribers", () => {
      const emitter = createEventEmitter();
      const callback1 = vi.fn();
      const callback2 = vi.fn();
      const callback3 = vi.fn();

      emitter.subscribe(callback1);
      emitter.subscribe(callback2);
      emitter.subscribe(callback3);
      emitter.emit("feature:started", { id: "123" });

      expect(callback1).toHaveBeenCalledOnce();
      expect(callback2).toHaveBeenCalledOnce();
      expect(callback3).toHaveBeenCalledOnce();
      expect(callback1).toHaveBeenCalledWith("feature:started", { id: "123" });
    });

    it("should support unsubscribe functionality", () => {
      const emitter = createEventEmitter();
      const callback = vi.fn();

      const unsubscribe = emitter.subscribe(callback);
      emitter.emit("agent:stream", { test: 1 });

      expect(callback).toHaveBeenCalledOnce();

      unsubscribe();
      emitter.emit("agent:stream", { test: 2 });

      expect(callback).toHaveBeenCalledOnce(); // Still called only once
    });

    it("should handle errors in subscribers without crashing", () => {
      const emitter = createEventEmitter();
      const errorCallback = vi.fn(() => {
        throw new Error("Subscriber error");
      });
      const normalCallback = vi.fn();
      const consoleSpy = vi.spyOn(console, "error").mockImplementation(() => {});

      emitter.subscribe(errorCallback);
      emitter.subscribe(normalCallback);

      expect(() => {
        emitter.emit("feature:error", { error: "test" });
      }).not.toThrow();

      expect(errorCallback).toHaveBeenCalledOnce();
      expect(normalCallback).toHaveBeenCalledOnce();
      expect(consoleSpy).toHaveBeenCalled();

      consoleSpy.mockRestore();
    });

    it("should emit different event types", () => {
      const emitter = createEventEmitter();
      const callback = vi.fn();

      emitter.subscribe(callback);

      const eventTypes: EventType[] = [
        "agent:stream",
        "auto-mode:started",
        "feature:completed",
        "project:analysis-progress",
      ];

      eventTypes.forEach((type) => {
        emitter.emit(type, { type });
      });

      expect(callback).toHaveBeenCalledTimes(4);
    });

    it("should handle emitting without subscribers", () => {
      const emitter = createEventEmitter();

      expect(() => {
        emitter.emit("agent:stream", { test: true });
      }).not.toThrow();
    });

    it("should allow multiple subscriptions and unsubscriptions", () => {
      const emitter = createEventEmitter();
      const callback1 = vi.fn();
      const callback2 = vi.fn();
      const callback3 = vi.fn();

      const unsub1 = emitter.subscribe(callback1);
      const unsub2 = emitter.subscribe(callback2);
      const unsub3 = emitter.subscribe(callback3);

      emitter.emit("feature:started", { test: 1 });
      expect(callback1).toHaveBeenCalledOnce();
      expect(callback2).toHaveBeenCalledOnce();
      expect(callback3).toHaveBeenCalledOnce();

      unsub2();

      emitter.emit("feature:started", { test: 2 });
      expect(callback1).toHaveBeenCalledTimes(2);
      expect(callback2).toHaveBeenCalledOnce(); // Still just once
      expect(callback3).toHaveBeenCalledTimes(2);

      unsub1();
      unsub3();

      emitter.emit("feature:started", { test: 3 });
      expect(callback1).toHaveBeenCalledTimes(2);
      expect(callback2).toHaveBeenCalledOnce();
      expect(callback3).toHaveBeenCalledTimes(2);
    });
  });
});