refactor: extract shared test helpers and improve test isolation

Extract createMockReq/createMockRes/createDefaults into shared
helpers/mock-res.ts to eliminate duplication between bedrock and
converse test suites.

Convert reasoning-all-providers from beforeAll/afterAll to
beforeEach/afterEach for proper per-test server isolation.

Author: jpr5

src/__tests__/helpers/mock-res.ts

@@ -0,0 +1,59 @@
+import * as http from "node:http";
+import type { HandlerDefaults } from "../../types.js";
+import { Logger } from "../../logger.js";
+
+export function createMockReq(overrides: Partial<http.IncomingMessage> = {}): http.IncomingMessage {
+  return {
+    method: undefined,
+    url: undefined,
+    headers: {},
+    ...overrides,
+  } as unknown as http.IncomingMessage;
+}
+
+export function createMockRes(): http.ServerResponse & {
+  _written: string;
+  _status: number;
+  _headers: Record<string, string>;
+} {
+  const res = {
+    _written: "",
+    _status: 0,
+    _headers: {} as Record<string, string>,
+    writableEnded: false,
+    statusCode: 0,
+    writeHead(status: number, headers?: Record<string, string>) {
+      res._status = status;
+      res.statusCode = status;
+      if (headers) Object.assign(res._headers, headers);
+    },
+    setHeader(name: string, value: string) {
+      res._headers[name] = value;
+    },
+    write(data: string) {
+      res._written += data;
+      return true;
+    },
+    end(data?: string) {
+      if (data) res._written += data;
+      res.writableEnded = true;
+    },
+    destroy() {
+      res.writableEnded = true;
+    },
+  };
+  return res as unknown as http.ServerResponse & {
+    _written: string;
+    _status: number;
+    _headers: Record<string, string>;
+  };
+}
+
+export function createDefaults(overrides: Partial<HandlerDefaults> = {}): HandlerDefaults {
+  return {
+    latency: 0,
+    chunkSize: 100,
+    logger: new Logger("silent"),
+    ...overrides,
+  };
+}

src/__tests__/reasoning-all-providers.test.ts

@@ -1,4 +1,4 @@
-import { describe, it, expect, beforeAll, afterAll } from "vitest";
+import { describe, it, expect, beforeEach, afterEach } from "vitest";
 import * as http from "node:http";
 import { crc32 } from "node:zlib";
 import type { Fixture } from "../types.js";
@@ -7,7 +7,7 @@ import { buildBedrockStreamTextEvents } from "../bedrock.js";
 
 // --- helpers ---
 
-let instance: ServerInstance;
+let instance: ServerInstance | null = null;
 let baseUrl: string;
 
 function post(
@@ -176,15 +176,18 @@ const allFixtures: Fixture[] = [reasoningFixture, plainFixture];
 
 // --- server lifecycle ---
 
-beforeAll(async () => {
+beforeEach(async () => {
   instance = await createServer(allFixtures);
   baseUrl = instance.url;
 });
 
-afterAll(async () => {
-  await new Promise<void>((resolve) => {
-    instance.server.close(() => resolve());
-  });
+afterEach(async () => {
+  if (instance) {
+    await new Promise<void>((resolve) => {
+      instance!.server.close(() => resolve());
+    });
+    instance = null;
+  }
 });
 
 // ─── OpenAI Chat Completions: Reasoning ─────────────────────────────────────
@@ -549,7 +552,9 @@ describe("POST /model/{id}/converse-stream (reasoning streaming)", () => {
       .join("");
     expect(fullThinking).toBe("Let me think step by step about this problem.");
 
-    expect(eventTypes[eventTypes.length - 1]).toBe("messageStop");
+    // metadata event (with usage) follows messageStop in the Converse stream
+    expect(eventTypes[eventTypes.length - 2]).toBe("messageStop");
+    expect(eventTypes[eventTypes.length - 1]).toBe("metadata");
   });
 
   it("no thinking block when reasoning is absent", async () => {