test: add server package tests

- Add resolveGinMode tests (debug, test, release, default modes)
- Add case sensitivity tests for mode resolution
- Server package coverage: 0% -> 3.2%
- Overall coverage: 54.2% -> 54.3%

internal/server/server_test.go

@@ -0,0 +1,39 @@
+package server
+
+import (
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+)
+
+// TestResolveGinMode 测试 Gin 模式解析
+func TestResolveGinMode(t *testing.T) {
+	tests := []struct {
+		name     string
+		mode     string
+		expected string
+	}{
+		{"debug", "debug", gin.DebugMode},
+		{"test", "test", gin.TestMode},
+		{"release", "release", gin.ReleaseMode},
+		{"empty", "", gin.ReleaseMode},
+		{"invalid", "invalid", gin.ReleaseMode},
+		{"other", "other", gin.ReleaseMode},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			got := resolveGinMode(tt.mode)
+			assert.Equal(t, tt.expected, got)
+		})
+	}
+}
+
+// TestResolveGinMode_CaseSensitivity 测试大小写敏感性
+func TestResolveGinMode_CaseSensitivity(t *testing.T) {
+	// 函数是区分大小写的
+	assert.Equal(t, gin.DebugMode, resolveGinMode("debug"))
+	assert.Equal(t, gin.ReleaseMode, resolveGinMode("DEBUG")) // 大写不匹配
+	assert.Equal(t, gin.ReleaseMode, resolveGinMode("Debug")) // 首字母大写不匹配
+}