feat: 新增 MySQL 数据库驱动支持，支持跨设备数据同步

backend/internal/database/database_test.go

@@ -0,0 +1,75 @@
+package database
+
+import (
+	"path/filepath"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"nex/backend/internal/config"
+)
+
+func TestInit_SQLite(t *testing.T) {
+	dir := t.TempDir()
+	cfg := &config.DatabaseConfig{
+		Driver:          "sqlite",
+		Path:            filepath.Join(dir, "test.db"),
+		MaxIdleConns:    5,
+		MaxOpenConns:    10,
+		ConnMaxLifetime: 0,
+	}
+
+	db, err := Init(cfg, nil)
+	require.NoError(t, err)
+	require.NotNil(t, db)
+	defer Close(db)
+
+	sqlDB, err := db.DB()
+	require.NoError(t, err)
+	require.NotNil(t, sqlDB)
+}
+
+func TestClose(t *testing.T) {
+	dir := t.TempDir()
+	cfg := &config.DatabaseConfig{
+		Driver:          "sqlite",
+		Path:            filepath.Join(dir, "test.db"),
+		MaxIdleConns:    5,
+		MaxOpenConns:    10,
+		ConnMaxLifetime: 0,
+	}
+
+	db, err := Init(cfg, nil)
+	require.NoError(t, err)
+	require.NotNil(t, db)
+
+	Close(db)
+}
+
+func TestBuildDSN(t *testing.T) {
+	cfg := &config.DatabaseConfig{
+		Driver:   "mysql",
+		Host:     "db.example.com",
+		Port:     3306,
+		User:     "nexuser",
+		Password: "secretpass",
+		DBName:   "nexdb",
+	}
+
+	dsn := BuildDSN(cfg)
+	assert.Equal(t, "nexuser:secretpass@tcp(db.example.com:3306)/nexdb?charset=utf8mb4&parseTime=true&loc=Local", dsn)
+}
+
+func TestBuildDSN_EmptyPassword(t *testing.T) {
+	cfg := &config.DatabaseConfig{
+		Driver: "mysql",
+		Host:   "localhost",
+		Port:   3306,
+		User:   "root",
+		DBName: "nex",
+	}
+
+	dsn := BuildDSN(cfg)
+	assert.Equal(t, "root:@tcp(localhost:3306)/nex?charset=utf8mb4&parseTime=true&loc=Local", dsn)
+}