test: add idempotency tests for initializeGlobalHookRunner (#50025)

src/plugins/hook-runner-global.test.ts

@@ -46,4 +46,54 @@ describe("hook-runner-global", () => {
     expect(modC.getGlobalHookRunner()).toBeNull();
     expect(modC.getGlobalPluginRegistry()).toBeNull();
   });
+
+  it("does not replace an existing runner that has typed hooks", async () => {
+    const mod = await importHookRunnerGlobalModule();
+    const registryWithHooks = createMockPluginRegistry([
+      { hookName: "llm_input", handler: vi.fn() },
+    ]);
+    const emptyRegistry = createMockPluginRegistry([]);
+
+    mod.initializeGlobalHookRunner(registryWithHooks);
+    const originalRunner = mod.getGlobalHookRunner();
+    expect(originalRunner?.hasHooks("llm_input")).toBe(true);
+
+    // Second call with empty registry should be a no-op
+    mod.initializeGlobalHookRunner(emptyRegistry);
+    expect(mod.getGlobalHookRunner()).toBe(originalRunner);
+    expect(mod.getGlobalPluginRegistry()).toBe(registryWithHooks);
+    expect(mod.getGlobalHookRunner()?.hasHooks("llm_input")).toBe(true);
+  });
+
+  it("allows replacing a runner that has no typed hooks", async () => {
+    const mod = await importHookRunnerGlobalModule();
+    const emptyRegistry = createMockPluginRegistry([]);
+    const registryWithHooks = createMockPluginRegistry([
+      { hookName: "llm_input", handler: vi.fn() },
+    ]);
+
+    mod.initializeGlobalHookRunner(emptyRegistry);
+    expect(mod.getGlobalHookRunner()?.hasHooks("llm_input")).toBe(false);
+
+    // Second call with hooks should replace
+    mod.initializeGlobalHookRunner(registryWithHooks);
+    expect(mod.getGlobalHookRunner()?.hasHooks("llm_input")).toBe(true);
+    expect(mod.getGlobalPluginRegistry()).toBe(registryWithHooks);
+  });
+
+  it("allows re-initialization after reset", async () => {
+    const mod = await importHookRunnerGlobalModule();
+    const registryA = createMockPluginRegistry([{ hookName: "llm_input", handler: vi.fn() }]);
+    const registryB = createMockPluginRegistry([{ hookName: "llm_output", handler: vi.fn() }]);
+
+    mod.initializeGlobalHookRunner(registryA);
+    expect(mod.getGlobalHookRunner()?.hasHooks("llm_input")).toBe(true);
+
+    mod.resetGlobalHookRunner();
+    expect(mod.getGlobalHookRunner()).toBeNull();
+
+    mod.initializeGlobalHookRunner(registryB);
+    expect(mod.getGlobalHookRunner()?.hasHooks("llm_output")).toBe(true);
+    expect(mod.getGlobalHookRunner()?.hasHooks("llm_input")).toBe(false);
+  });
 });