From 71c4e61735affd417827c329ac92761331bbadf8 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Hartmut=20N=C3=B6renberg?= <hn@hartmut-noerenberg.com>
Date: Wed, 1 Apr 2026 09:10:45 +0200
Subject: [PATCH] test(web): cover timeline sse edge paths

---
 apps/web/src/hooks/useTimelineSSE.test.ts | 137 ++++++++++++++++++++++
 1 file changed, 137 insertions(+)
 create mode 100644 apps/web/src/hooks/useTimelineSSE.test.ts

diff --git a/apps/web/src/hooks/useTimelineSSE.test.ts b/apps/web/src/hooks/useTimelineSSE.test.ts
new file mode 100644
index 0000000..f891116
--- /dev/null
+++ b/apps/web/src/hooks/useTimelineSSE.test.ts
@@ -0,0 +1,137 @@
+import { SSE_EVENT_TYPES } from "@capakraken/shared";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
+
+const invalidateQueries = vi.fn();
+const effectCleanups: Array<() => void> = [];
+
+vi.mock("@tanstack/react-query", () => ({
+  useQueryClient: () => ({
+    invalidateQueries,
+  }),
+}));
+
+vi.mock("react", async () => {
+  const actual = await vi.importActual<typeof import("react")>("react");
+  return {
+    ...actual,
+    useEffect: (callback: () => void | (() => void)) => {
+      const cleanup = callback();
+      if (typeof cleanup === "function") {
+        effectCleanups.push(cleanup);
+      }
+    },
+    useRef: <T,>(value: T) => ({ current: value }),
+  };
+});
+
+import { useTimelineSSE } from "./useTimelineSSE.js";
+
+class MockEventSource {
+  static instances: MockEventSource[] = [];
+
+  onopen: (() => void) | null = null;
+  onmessage: ((event: MessageEvent) => void) | null = null;
+  onerror: (() => void) | null = null;
+  close = vi.fn();
+
+  constructor(public readonly url: string) {
+    MockEventSource.instances.push(this);
+  }
+
+  emitOpen() {
+    this.onopen?.();
+  }
+
+  emitMessage(data: string) {
+    this.onmessage?.({ data } as MessageEvent);
+  }
+
+  emitError() {
+    this.onerror?.();
+  }
+}
+
+describe("useTimelineSSE", () => {
+  beforeEach(() => {
+    vi.useFakeTimers();
+    vi.clearAllMocks();
+    effectCleanups.length = 0;
+    MockEventSource.instances.length = 0;
+    vi.stubGlobal("EventSource", MockEventSource);
+  });
+
+  afterEach(() => {
+    while (effectCleanups.length > 0) {
+      effectCleanups.pop()?.();
+    }
+    vi.unstubAllGlobals();
+    vi.useRealTimers();
+  });
+
+  it("ignores malformed SSE payloads without invalidating queries", () => {
+    useTimelineSSE();
+
+    expect(MockEventSource.instances).toHaveLength(1);
+
+    MockEventSource.instances[0]?.emitMessage("{not-json");
+
+    expect(invalidateQueries).not.toHaveBeenCalled();
+  });
+
+  it("does not invalidate queries for ping messages", () => {
+    useTimelineSSE();
+
+    expect(MockEventSource.instances).toHaveLength(1);
+
+    MockEventSource.instances[0]?.emitMessage(JSON.stringify({ type: SSE_EVENT_TYPES.PING }));
+
+    expect(invalidateQueries).not.toHaveBeenCalled();
+  });
+
+  it("resets reconnect backoff after ping and reconnects only once per pending timer", () => {
+    useTimelineSSE();
+
+    const firstConnection = MockEventSource.instances[0];
+    expect(firstConnection).toBeDefined();
+
+    firstConnection?.emitError();
+    firstConnection?.emitError();
+    expect(firstConnection?.close).toHaveBeenCalledTimes(2);
+
+    vi.advanceTimersByTime(1999);
+    expect(MockEventSource.instances).toHaveLength(1);
+
+    vi.advanceTimersByTime(1);
+    expect(MockEventSource.instances).toHaveLength(2);
+
+    const secondConnection = MockEventSource.instances[1];
+    secondConnection?.emitMessage(JSON.stringify({ type: SSE_EVENT_TYPES.PING }));
+    secondConnection?.emitError();
+
+    vi.advanceTimersByTime(1999);
+    expect(MockEventSource.instances).toHaveLength(2);
+
+    vi.advanceTimersByTime(1);
+    expect(MockEventSource.instances).toHaveLength(3);
+
+    expect(invalidateQueries).not.toHaveBeenCalled();
+  });
+
+  it("clears a pending reconnect when the hook is disposed", () => {
+    useTimelineSSE();
+
+    const firstConnection = MockEventSource.instances[0];
+    expect(firstConnection).toBeDefined();
+
+    firstConnection?.emitError();
+
+    while (effectCleanups.length > 0) {
+      effectCleanups.pop()?.();
+    }
+
+    vi.advanceTimersByTime(30_000);
+
+    expect(MockEventSource.instances).toHaveLength(1);
+    expect(firstConnection?.close).toHaveBeenCalled();
+  });
+});