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`sse.test.ts`

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febd4f0Claude	1	/**
	2	* Unit tests for src/lib/sse.ts — the in-process pub/sub broadcaster.
	3	*
	4	* These tests exercise the pure module-level state. Because the registry is
	5	* a module-level `Map`, each test uses a unique topic name so cross-test
	6	* leakage is impossible; we also explicitly unsubscribe everything we
	7	* subscribe.
	8	*/
	9
	10	import { describe, it, expect } from "bun:test";
	11	import {
	12	publish,
	13	subscribe,
	14	topicSubscriberCount,
	15	type SSEEvent,
	16	} from "../lib/sse";
	17
	18	describe("sse broadcaster", () => {
	19	it("publish with no subscribers is a no-op", () => {
	20	// No throw, no side effect. topicSubscriberCount stays zero.
	21	expect(() =>
	22	publish("repo:no-subs", { data: { hello: "world" } })
	23	).not.toThrow();
	24	expect(topicSubscriberCount("repo:no-subs")).toBe(0);
	25	});
	26
	27	it("a subscriber receives events published to its topic", () => {
	28	const received: SSEEvent[] = [];
	29	const unsub = subscribe("repo:alpha", (e) => received.push(e));
	30
	31	expect(topicSubscriberCount("repo:alpha")).toBe(1);
	32
	33	publish("repo:alpha", { event: "push", data: { sha: "deadbeef" } });
	34	publish("repo:alpha", { event: "star", data: { count: 7 }, id: "42" });
	35
	36	expect(received).toHaveLength(2);
	37	expect(received[0]?.event).toBe("push");
	38	expect((received[0]?.data as any).sha).toBe("deadbeef");
	39	expect(received[1]?.id).toBe("42");
	40
	41	unsub();
	42	expect(topicSubscriberCount("repo:alpha")).toBe(0);
	43	});
	44
	45	it("multiple subscribers on the same topic all receive each event", () => {
	46	const a: SSEEvent[] = [];
	47	const b: SSEEvent[] = [];
	48	const c: SSEEvent[] = [];
	49	const unsubA = subscribe("pr:beta", (e) => a.push(e));
	50	const unsubB = subscribe("pr:beta", (e) => b.push(e));
	51	const unsubC = subscribe("pr:beta", (e) => c.push(e));
	52
	53	expect(topicSubscriberCount("pr:beta")).toBe(3);
	54
	55	publish("pr:beta", { event: "review", data: "submitted" });
	56
	57	expect(a).toHaveLength(1);
	58	expect(b).toHaveLength(1);
	59	expect(c).toHaveLength(1);
	60	expect(a[0]?.data).toBe("submitted");
	61
	62	unsubA();
	63	unsubB();
	64	unsubC();
	65	expect(topicSubscriberCount("pr:beta")).toBe(0);
	66	});
	67
	68	it("unsubscribe stops delivery for that handler only", () => {
	69	const keeper: SSEEvent[] = [];
	70	const leaver: SSEEvent[] = [];
	71	const unsubKeeper = subscribe("user:gamma", (e) => keeper.push(e));
	72	const unsubLeaver = subscribe("user:gamma", (e) => leaver.push(e));
	73
	74	publish("user:gamma", { data: "first" });
	75	expect(keeper).toHaveLength(1);
	76	expect(leaver).toHaveLength(1);
	77
	78	unsubLeaver();
	79	expect(topicSubscriberCount("user:gamma")).toBe(1);
	80
	81	publish("user:gamma", { data: "second" });
	82	expect(keeper).toHaveLength(2);
	83	expect(leaver).toHaveLength(1); // unchanged — leaver is gone
	84
	85	unsubKeeper();
	86	expect(topicSubscriberCount("user:gamma")).toBe(0);
	87
	88	// Topic entry should be cleaned up after last unsubscribe.
	89	publish("user:gamma", { data: "third" });
	90	expect(keeper).toHaveLength(2);
	91	});
	92
	93	it("a throwing handler does not prevent other handlers from receiving", () => {
	94	const good: SSEEvent[] = [];
	95	const unsubBad = subscribe("repo:delta", () => {
	96	throw new Error("boom");
	97	});
	98	const unsubGood = subscribe("repo:delta", (e) => good.push(e));
	99
	100	expect(() =>
	101	publish("repo:delta", { data: "payload" })
	102	).not.toThrow();
	103	expect(good).toHaveLength(1);
	104
	105	unsubBad();
	106	unsubGood();
	107	});
	108	});