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/internal/conversion/engine_supplemental_test.go

@@ -321,3 +321,58 @@ func (m *testMiddleware) InterceptStreamEvent(event *canonical.CanonicalStreamEv
 }
 
 var _ = json.Marshal
+
+func TestConvertEmbeddingBody_DecodeError(t *testing.T) {
+	registry := NewMemoryRegistry()
+	engine := NewConversionEngine(registry, nil)
+
+	clientAdapter := newMockAdapter("client", false)
+	clientAdapter.decodeEmbeddingReqFn = func(raw []byte) (*canonical.CanonicalEmbeddingRequest, error) {
+		return nil, errors.New("decode embedding failed")
+	}
+	clientAdapter.supportsIface = map[InterfaceType]bool{InterfaceTypeEmbeddings: true}
+	providerAdapter := newMockAdapter("provider", false)
+	providerAdapter.supportsIface = map[InterfaceType]bool{InterfaceTypeEmbeddings: true}
+	_ = engine.RegisterAdapter(clientAdapter)
+	_ = engine.RegisterAdapter(providerAdapter)
+
+	body := []byte(`{"model":"text-embedding","input":"hello"}`)
+	result, err := engine.convertEmbeddingBody(clientAdapter, providerAdapter, NewTargetProvider("", "", ""), body)
+	require.NoError(t, err)
+	assert.Equal(t, body, result)
+}
+
+func TestConvertRerankBody_DecodeError(t *testing.T) {
+	registry := NewMemoryRegistry()
+	engine := NewConversionEngine(registry, nil)
+
+	clientAdapter := newMockAdapter("client", false)
+	clientAdapter.decodeRerankReqFn = func(raw []byte) (*canonical.CanonicalRerankRequest, error) {
+		return nil, errors.New("decode rerank failed")
+	}
+	clientAdapter.supportsIface = map[InterfaceType]bool{InterfaceTypeRerank: true}
+	providerAdapter := newMockAdapter("provider", false)
+	providerAdapter.supportsIface = map[InterfaceType]bool{InterfaceTypeRerank: true}
+	_ = engine.RegisterAdapter(clientAdapter)
+	_ = engine.RegisterAdapter(providerAdapter)
+
+	body := []byte(`{"model":"rerank","query":"test","documents":["a"]}`)
+	result, err := engine.convertRerankBody(clientAdapter, providerAdapter, NewTargetProvider("", "", ""), body)
+	require.NoError(t, err)
+	assert.Equal(t, body, result)
+}
+
+func TestConvertBody_UnknownInterfaceType(t *testing.T) {
+	registry := NewMemoryRegistry()
+	engine := NewConversionEngine(registry, nil)
+
+	clientAdapter := newMockAdapter("client", false)
+	providerAdapter := newMockAdapter("provider", false)
+	_ = engine.RegisterAdapter(clientAdapter)
+	_ = engine.RegisterAdapter(providerAdapter)
+
+	body := []byte(`{"test":"data"}`)
+	result, err := engine.convertBody(InterfaceType("UNKNOWN"), clientAdapter, providerAdapter, NewTargetProvider("", "", ""), body)
+	require.NoError(t, err)
+	assert.Equal(t, body, result)
+}

backend/internal/conversion/engine_test.go

@@ -13,18 +13,20 @@ import (
 
 // mockProtocolAdapter 模拟协议适配器
 type mockProtocolAdapter struct {
-	protocolName     string
-	passthrough      bool
-	ifaceType        InterfaceType
-	supportsIface    map[InterfaceType]bool
-	decodeReqFn      func([]byte) (*canonical.CanonicalRequest, error)
-	encodeReqFn      func(*canonical.CanonicalRequest, *TargetProvider) ([]byte, error)
-	decodeRespFn     func([]byte) (*canonical.CanonicalResponse, error)
-	encodeRespFn     func(*canonical.CanonicalResponse) ([]byte, error)
-	streamDecoderFn  func() StreamDecoder
-	streamEncoderFn  func() StreamEncoder
-	rewriteReqFn     func([]byte, string, InterfaceType) ([]byte, error)
-	rewriteRespFn    func([]byte, string, InterfaceType) ([]byte, error)
+	protocolName         string
+	passthrough          bool
+	ifaceType            InterfaceType
+	supportsIface        map[InterfaceType]bool
+	decodeReqFn          func([]byte) (*canonical.CanonicalRequest, error)
+	encodeReqFn          func(*canonical.CanonicalRequest, *TargetProvider) ([]byte, error)
+	decodeRespFn         func([]byte) (*canonical.CanonicalResponse, error)
+	encodeRespFn         func(*canonical.CanonicalResponse) ([]byte, error)
+	streamDecoderFn      func() StreamDecoder
+	streamEncoderFn      func() StreamEncoder
+	rewriteReqFn         func([]byte, string, InterfaceType) ([]byte, error)
+	rewriteRespFn        func([]byte, string, InterfaceType) ([]byte, error)
+	decodeEmbeddingReqFn func([]byte) (*canonical.CanonicalEmbeddingRequest, error)
+	decodeRerankReqFn    func([]byte) (*canonical.CanonicalRerankRequest, error)
 }
 
 func newMockAdapter(name string, passthrough bool) *mockProtocolAdapter {
@@ -126,6 +128,9 @@ func (m *mockProtocolAdapter) EncodeModelInfoResponse(info *canonical.CanonicalM
 }
 
 func (m *mockProtocolAdapter) DecodeEmbeddingRequest(raw []byte) (*canonical.CanonicalEmbeddingRequest, error) {
+	if m.decodeEmbeddingReqFn != nil {
+		return m.decodeEmbeddingReqFn(raw)
+	}
 	return &canonical.CanonicalEmbeddingRequest{}, nil
 }
 
@@ -142,6 +147,9 @@ func (m *mockProtocolAdapter) EncodeEmbeddingResponse(resp *canonical.CanonicalE
 }
 
 func (m *mockProtocolAdapter) DecodeRerankRequest(raw []byte) (*canonical.CanonicalRerankRequest, error) {
+	if m.decodeRerankReqFn != nil {
+		return m.decodeRerankReqFn(raw)
+	}
 	return &canonical.CanonicalRerankRequest{}, nil
 }
 

backend/internal/conversion/openai/decoder_test.go

@@ -409,3 +409,25 @@ func TestDecodeResponse_Refusal(t *testing.T) {
 	}
 	assert.True(t, found)
 }
+
+func TestDecodeRequest_AssistantContentArray(t *testing.T) {
+	body := []byte(`{
+		"model": "gpt-4",
+		"messages": [
+			{"role": "user", "content": "hello"},
+			{
+				"role": "assistant",
+				"content": [{"type": "text", "text": "hello back"}]
+			}
+		]
+	}`)
+
+	req, err := decodeRequest(body)
+	require.NoError(t, err)
+	assert.Len(t, req.Messages, 2)
+	assistantMsg := req.Messages[1]
+	assert.Equal(t, canonical.RoleAssistant, assistantMsg.Role)
+	assert.Len(t, assistantMsg.Content, 1)
+	assert.Equal(t, "text", assistantMsg.Content[0].Type)
+	assert.Equal(t, "hello back", assistantMsg.Content[0].Text)
+}