refactor: unify typing dispatch lifecycle and policy boundaries

src/channels/typing-start-guard.test.ts

@@ -0,0 +1,65 @@
+import { describe, expect, it, vi } from "vitest";
+import { createTypingStartGuard } from "./typing-start-guard.js";
+
+describe("createTypingStartGuard", () => {
+  it("skips starts when sealed", async () => {
+    const start = vi.fn();
+    const guard = createTypingStartGuard({
+      isSealed: () => true,
+    });
+
+    const result = await guard.run(start);
+    expect(result).toBe("skipped");
+    expect(start).not.toHaveBeenCalled();
+  });
+
+  it("trips breaker after max consecutive failures", async () => {
+    const onStartError = vi.fn();
+    const onTrip = vi.fn();
+    const guard = createTypingStartGuard({
+      isSealed: () => false,
+      onStartError,
+      onTrip,
+      maxConsecutiveFailures: 2,
+    });
+    const start = vi.fn().mockRejectedValue(new Error("fail"));
+
+    const first = await guard.run(start);
+    const second = await guard.run(start);
+    const third = await guard.run(start);
+
+    expect(first).toBe("failed");
+    expect(second).toBe("tripped");
+    expect(third).toBe("skipped");
+    expect(onStartError).toHaveBeenCalledTimes(2);
+    expect(onTrip).toHaveBeenCalledTimes(1);
+  });
+
+  it("resets breaker state", async () => {
+    const guard = createTypingStartGuard({
+      isSealed: () => false,
+      maxConsecutiveFailures: 1,
+    });
+    const failStart = vi.fn().mockRejectedValue(new Error("fail"));
+    const okStart = vi.fn().mockResolvedValue(undefined);
+
+    const trip = await guard.run(failStart);
+    expect(trip).toBe("tripped");
+    expect(guard.isTripped()).toBe(true);
+
+    guard.reset();
+    const started = await guard.run(okStart);
+    expect(started).toBe("started");
+    expect(guard.isTripped()).toBe(false);
+  });
+
+  it("rethrows start errors when configured", async () => {
+    const guard = createTypingStartGuard({
+      isSealed: () => false,
+      rethrowOnError: true,
+    });
+    const start = vi.fn().mockRejectedValue(new Error("boom"));
+
+    await expect(guard.run(start)).rejects.toThrow("boom");
+  });
+});