test(server): 完善 server 模块测试覆盖率

覆盖率从 44.2% 提升至 45.8%，新增测试：
- TestPoolWrapHandler: 协程池处理器包装测试
- TestPoolWrapHandler_WhenStopped: 池停止时包装测试
- TestServer_Proxies: 代理管理测试
- TestServer_Running: 运行状态测试
- TestServer_StopWithNilFastServer: 无服务器停止测试
- TestServer_GracefulStopWithNilFastServer: 无服务器优雅停止测试
- TestServer_GetProxyCacheStats: 代理缓存统计测试
- TestServer_BuildMiddlewareChain_EmptyConfig: 空配置中间件链测试
- TestServer_TrackStats_EmptyBody: 空响应体统计测试

注：Start/startSingleMode 等启动函数适合集成测试

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

internal/server/pool_test.go

@@ -168,3 +168,59 @@ func TestPoolSubmitWhenStopped(t *testing.T) {
 		t.Error("Expected task to be executed directly when pool is stopped")
 	}
 }
+
+func TestPoolWrapHandler(t *testing.T) {
+	p := NewGoroutinePool(PoolConfig{
+		MaxWorkers:  10,
+		MinWorkers:  2,
+		QueueSize:   10,
+		IdleTimeout: 5 * time.Second,
+	})
+
+	p.Start()
+	defer p.Stop()
+
+	var executed atomic.Bool
+	originalHandler := func(ctx *fasthttp.RequestCtx) {
+		executed.Store(true)
+		ctx.SetBodyString("wrapped response")
+	}
+
+	wrappedHandler := p.WrapHandler(originalHandler)
+
+	ctx := &fasthttp.RequestCtx{}
+	ctx.Init(&fasthttp.Request{}, nil, nil)
+
+	wrappedHandler(ctx)
+
+	// 等待异步执行
+	time.Sleep(100 * time.Millisecond)
+
+	if !executed.Load() {
+		t.Error("Expected wrapped handler to be executed")
+	}
+}
+
+func TestPoolWrapHandler_WhenStopped(t *testing.T) {
+	p := NewGoroutinePool(PoolConfig{
+		MaxWorkers: 10,
+	})
+	// 不启动池
+
+	var executed atomic.Bool
+	originalHandler := func(ctx *fasthttp.RequestCtx) {
+		executed.Store(true)
+	}
+
+	wrappedHandler := p.WrapHandler(originalHandler)
+
+	ctx := &fasthttp.RequestCtx{}
+	ctx.Init(&fasthttp.Request{}, nil, nil)
+
+	wrappedHandler(ctx)
+
+	// 池停止时应该直接执行
+	if !executed.Load() {
+		t.Error("Expected handler to be executed directly when pool is stopped")
+	}
+}

internal/server/server_test.go

@@ -488,3 +488,139 @@ func TestServer_Connections(t *testing.T) {
 		t.Errorf("Expected 0 connections, got %d", s.connections.Load())
 	}
 }
+
+// TestServer_Proxies 测试代理管理
+func TestServer_Proxies(t *testing.T) {
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Listen: ":8080",
+		},
+	}
+
+	s := New(cfg)
+
+	// 初始代理列表应为空
+	if len(s.proxies) != 0 {
+		t.Error("Initial proxies should be empty")
+	}
+}
+
+// TestServer_Running 测试运行状态
+func TestServer_Running(t *testing.T) {
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Listen: ":8080",
+		},
+	}
+
+	s := New(cfg)
+
+	// 初始状态应为未运行
+	if s.running {
+		t.Error("Initial running state should be false")
+	}
+}
+
+// TestServer_StopWithNilFastServer 测试无 fastServer 时停止
+func TestServer_StopWithNilFastServer(t *testing.T) {
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Listen: ":8080",
+		},
+	}
+
+	s := New(cfg)
+	s.fastServer = nil
+
+	err := s.Stop()
+	if err != nil {
+		t.Errorf("Stop with nil fastServer should succeed: %v", err)
+	}
+}
+
+// TestServer_GracefulStopWithNilFastServer 测试无 fastServer 时优雅停止
+func TestServer_GracefulStopWithNilFastServer(t *testing.T) {
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Listen: ":8080",
+		},
+	}
+
+	s := New(cfg)
+	s.fastServer = nil
+
+	err := s.GracefulStop(5 * time.Second)
+	if err != nil {
+		t.Errorf("GracefulStop with nil fastServer should succeed: %v", err)
+	}
+}
+
+// TestServer_GetProxyCacheStats 测试代理缓存统计
+func TestServer_GetProxyCacheStats(t *testing.T) {
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Listen: ":8080",
+		},
+	}
+
+	s := New(cfg)
+
+	// 无代理时应返回空统计
+	stats := s.getProxyCacheStats()
+	if stats.Entries != 0 {
+		t.Errorf("Expected 0 entries, got %d", stats.Entries)
+	}
+	if stats.Pending != 0 {
+		t.Errorf("Expected 0 pending, got %d", stats.Pending)
+	}
+}
+
+// TestServer_BuildMiddlewareChain_EmptyConfig 测试空配置的中间件链
+func TestServer_BuildMiddlewareChain_EmptyConfig(t *testing.T) {
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Listen: ":8080",
+		},
+	}
+
+	s := New(cfg)
+
+	chain, err := s.buildMiddlewareChain(&cfg.Server)
+	if err != nil {
+		t.Errorf("Unexpected error: %v", err)
+	}
+	if chain == nil {
+		t.Error("Expected non-nil chain")
+	}
+}
+
+// TestServer_TrackStats_EmptyBody 测试空响应体的统计
+func TestServer_TrackStats_EmptyBody(t *testing.T) {
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Listen: ":8080",
+		},
+	}
+
+	s := New(cfg)
+
+	handler := func(ctx *fasthttp.RequestCtx) {
+		// 空响应
+	}
+
+	wrappedHandler := s.trackStats(handler)
+
+	ctx := &fasthttp.RequestCtx{}
+	ctx.Init(&fasthttp.Request{}, nil, nil)
+	ctx.Request.SetBody(nil)
+
+	wrappedHandler(ctx)
+
+	if s.requests.Load() != 1 {
+		t.Errorf("Expected 1 request, got %d", s.requests.Load())
+	}
+
+	if s.bytesSent.Load() != 0 {
+		t.Errorf("Expected 0 bytes sent, got %d", s.bytesSent.Load())
+	}
+}