feat: 系统性改进后端测试体系

- 新增 6 个测试场景 (config load pipe, handler errors, service aggregation, engine degradation, openai decoder edges, negative tests)
- 更新测试工具规格 (mockgen, in-memory SQLite)
- 覆盖率目标从 >80% 提升至 >85%
- 新增 test-unit 和 test-integration Makefile 命令
- 新增死代码清理和 mockgen 需求
- 归档变更至 openspec/changes/archive/2026-04-22-improve-backend-testing/

backend/tests/config/config_test.go

@@ -0,0 +1,193 @@
+package config
+
+import (
+	"os"
+	"path/filepath"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	"nex/backend/internal/config"
+)
+
+func TestLoadConfig_DefaultValues(t *testing.T) {
+	tmpDir := t.TempDir()
+	configPath := filepath.Join(tmpDir, "config.yaml")
+
+	cfg, err := config.LoadConfigFromPath(configPath)
+	require.NoError(t, err)
+
+	assert.Equal(t, 9826, cfg.Server.Port)
+	assert.Equal(t, 30*time.Second, cfg.Server.ReadTimeout)
+	assert.Equal(t, 30*time.Second, cfg.Server.WriteTimeout)
+
+	assert.Equal(t, 10, cfg.Database.MaxIdleConns)
+	assert.Equal(t, 100, cfg.Database.MaxOpenConns)
+	assert.Equal(t, 1*time.Hour, cfg.Database.ConnMaxLifetime)
+
+	assert.Equal(t, "info", cfg.Log.Level)
+	assert.Equal(t, 100, cfg.Log.MaxSize)
+	assert.Equal(t, 10, cfg.Log.MaxBackups)
+	assert.Equal(t, 30, cfg.Log.MaxAge)
+	assert.True(t, cfg.Log.Compress)
+}
+
+func TestLoadConfig_EnvOverride(t *testing.T) {
+	tmpDir := t.TempDir()
+	configPath := filepath.Join(tmpDir, "config.yaml")
+
+	t.Setenv("NEX_SERVER_PORT", "9000")
+	t.Setenv("NEX_LOG_LEVEL", "debug")
+	t.Setenv("NEX_DATABASE_MAX_IDLE_CONNS", "20")
+
+	cfg, err := config.LoadConfigFromPath(configPath)
+	require.NoError(t, err)
+
+	assert.Equal(t, 9000, cfg.Server.Port)
+	assert.Equal(t, "debug", cfg.Log.Level)
+	assert.Equal(t, 20, cfg.Database.MaxIdleConns)
+}
+
+func TestLoadConfig_YAMLFile(t *testing.T) {
+	tmpDir := t.TempDir()
+	configPath := filepath.Join(tmpDir, "config.yaml")
+
+	yamlContent := `
+server:
+  port: 8080
+  read_timeout: 60s
+  write_timeout: 60s
+database:
+  path: /custom/path.db
+  max_idle_conns: 5
+  max_open_conns: 50
+  conn_max_lifetime: 2h
+log:
+  level: warn
+  path: /custom/log
+  max_size: 200
+  max_backups: 5
+  max_age: 7
+  compress: false
+`
+	err := os.WriteFile(configPath, []byte(yamlContent), 0644)
+	require.NoError(t, err)
+
+	cfg, err := config.LoadConfigFromPath(configPath)
+	require.NoError(t, err)
+
+	assert.Equal(t, 8080, cfg.Server.Port)
+	assert.Equal(t, 60*time.Second, cfg.Server.ReadTimeout)
+	assert.Equal(t, 60*time.Second, cfg.Server.WriteTimeout)
+	assert.Equal(t, "/custom/path.db", cfg.Database.Path)
+	assert.Equal(t, 5, cfg.Database.MaxIdleConns)
+	assert.Equal(t, 50, cfg.Database.MaxOpenConns)
+	assert.Equal(t, 2*time.Hour, cfg.Database.ConnMaxLifetime)
+	assert.Equal(t, "warn", cfg.Log.Level)
+	assert.Equal(t, "/custom/log", cfg.Log.Path)
+	assert.Equal(t, 200, cfg.Log.MaxSize)
+	assert.Equal(t, 5, cfg.Log.MaxBackups)
+	assert.Equal(t, 7, cfg.Log.MaxAge)
+	assert.False(t, cfg.Log.Compress)
+}
+
+func TestLoadConfig_PriorityChain(t *testing.T) {
+	tmpDir := t.TempDir()
+	configPath := filepath.Join(tmpDir, "config.yaml")
+
+	yamlContent := `
+server:
+  port: 8080
+log:
+  level: warn
+`
+	err := os.WriteFile(configPath, []byte(yamlContent), 0644)
+	require.NoError(t, err)
+
+	t.Setenv("NEX_SERVER_PORT", "9000")
+
+	originalArgs := os.Args
+	defer func() { os.Args = originalArgs }()
+	os.Args = []string{"test", "--server-port", "9999"}
+
+	cfg, err := config.LoadConfigFromPath(configPath)
+	require.NoError(t, err)
+
+	assert.Equal(t, 9999, cfg.Server.Port, "CLI should override ENV and YAML")
+	assert.Equal(t, "warn", cfg.Log.Level, "YAML value should be used when no CLI/ENV override")
+}
+
+func TestLoadConfig_AutoCreate(t *testing.T) {
+	tmpDir := t.TempDir()
+	configPath := filepath.Join(tmpDir, "config.yaml")
+
+	_, err := os.Stat(configPath)
+	assert.True(t, os.IsNotExist(err), "config file should not exist before load")
+
+	cfg, err := config.LoadConfigFromPath(configPath)
+	require.NoError(t, err)
+	require.NotNil(t, cfg)
+
+	assert.Equal(t, 9826, cfg.Server.Port, "should load with default values")
+}
+
+func TestSaveAndLoadConfig(t *testing.T) {
+	tmpDir := t.TempDir()
+
+	homeDir, err := os.UserHomeDir()
+	require.NoError(t, err)
+	nexDir := filepath.Join(homeDir, ".nex")
+	configPath := filepath.Join(nexDir, "config.yaml")
+
+	originalConfig, err := os.ReadFile(configPath)
+	if err != nil && !os.IsNotExist(err) {
+		require.NoError(t, err)
+	}
+	defer func() {
+		if originalConfig != nil {
+			_ = os.WriteFile(configPath, originalConfig, 0644)
+		}
+	}()
+
+	cfg := &config.Config{
+		Server: config.ServerConfig{
+			Port:         7777,
+			ReadTimeout:  45 * time.Second,
+			WriteTimeout: 45 * time.Second,
+		},
+		Database: config.DatabaseConfig{
+			Path:            filepath.Join(tmpDir, "test.db"),
+			MaxIdleConns:    15,
+			MaxOpenConns:    150,
+			ConnMaxLifetime: 2 * time.Hour,
+		},
+		Log: config.LogConfig{
+			Level:      "debug",
+			Path:       filepath.Join(tmpDir, "log"),
+			MaxSize:    50,
+			MaxBackups: 3,
+			MaxAge:     14,
+			Compress:   false,
+		},
+	}
+
+	err = config.SaveConfig(cfg)
+	require.NoError(t, err)
+
+	loaded, err := config.LoadConfig()
+	require.NoError(t, err)
+
+	assert.Equal(t, cfg.Server.Port, loaded.Server.Port)
+	assert.Equal(t, cfg.Server.ReadTimeout, loaded.Server.ReadTimeout)
+	assert.Equal(t, cfg.Server.WriteTimeout, loaded.Server.WriteTimeout)
+	assert.Equal(t, cfg.Database.MaxIdleConns, loaded.Database.MaxIdleConns)
+	assert.Equal(t, cfg.Database.MaxOpenConns, loaded.Database.MaxOpenConns)
+	assert.Equal(t, cfg.Database.ConnMaxLifetime, loaded.Database.ConnMaxLifetime)
+	assert.Equal(t, cfg.Log.Level, loaded.Log.Level)
+	assert.Equal(t, cfg.Log.MaxSize, loaded.Log.MaxSize)
+	assert.Equal(t, cfg.Log.MaxBackups, loaded.Log.MaxBackups)
+	assert.Equal(t, cfg.Log.MaxAge, loaded.Log.MaxAge)
+	assert.Equal(t, cfg.Log.Compress, loaded.Log.Compress)
+}