feat(backend): 提交后端审计修复与配套测试改动

backend/internal/handler/gateway_handler_error_fallback_test.go

@@ -0,0 +1,49 @@
+package handler
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGatewayEnsureForwardErrorResponse_WritesFallbackWhenNotWritten(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodGet, "/", nil)
+
+	h := &GatewayHandler{}
+	wrote := h.ensureForwardErrorResponse(c, false)
+
+	require.True(t, wrote)
+	require.Equal(t, http.StatusBadGateway, w.Code)
+
+	var parsed map[string]any
+	err := json.Unmarshal(w.Body.Bytes(), &parsed)
+	require.NoError(t, err)
+	assert.Equal(t, "error", parsed["type"])
+	errorObj, ok := parsed["error"].(map[string]any)
+	require.True(t, ok)
+	assert.Equal(t, "upstream_error", errorObj["type"])
+	assert.Equal(t, "Upstream request failed", errorObj["message"])
+}
+
+func TestGatewayEnsureForwardErrorResponse_DoesNotOverrideWrittenResponse(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	w := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(w)
+	c.Request = httptest.NewRequest(http.MethodGet, "/", nil)
+	c.String(http.StatusTeapot, "already written")
+
+	h := &GatewayHandler{}
+	wrote := h.ensureForwardErrorResponse(c, false)
+
+	require.False(t, wrote)
+	require.Equal(t, http.StatusTeapot, w.Code)
+	assert.Equal(t, "already written", w.Body.String())
+}