feat(v0.912): Cashflow - payment E2E integration tests

- Add MarketplaceServiceOverride and AuthMiddlewareOverride to config for tests
- Wire overrides in routes_webhooks and routes_marketplace (authForMarketplaceInterface)
- payment_flow_test: cart -> checkout -> webhook -> order completed, license, transfer
- webhook_idempotency_test: 3 identical webhooks -> 1 order, 1 license
- webhook_security_test: empty secret 500, invalid sig 401, valid sig 200
- refund_flow_test: completed order -> refund -> order refunded, license revoked
- Shared computeWebhookSignature helper in webhook_test_helpers.go
- SetMaxOpenConns(1) for sqlite :memory: in idempotency test to avoid flakiness

Ref: docs/ROADMAP_V09XX_TO_V1.md v0.912 Cashflow

VERSION

@@ -1 +1 @@
-0.911
+0.912

veza-backend-api/internal/api/routes_marketplace.go

@@ -8,10 +8,25 @@ import (
 	"veza-backend-api/internal/config"
 	"veza-backend-api/internal/core/marketplace"
 	"veza-backend-api/internal/handlers"
+	"veza-backend-api/internal/middleware"
 	"veza-backend-api/internal/services"
 	"veza-backend-api/internal/services/hyperswitch"
 )
 
+// authForMarketplaceInterface has the auth methods needed by marketplace routes (allows test overrides)
+type authForMarketplaceInterface interface {
+	RequireAuth() gin.HandlerFunc
+	RequireContentCreatorRole() gin.HandlerFunc
+	RequireOwnershipOrAdmin(string, middleware.ResourceOwnerResolver) gin.HandlerFunc
+}
+
+func (r *APIRouter) authForMarketplace() authForMarketplaceInterface {
+	if r.config.AuthMiddlewareOverride != nil {
+		return r.config.AuthMiddlewareOverride.(authForMarketplaceInterface)
+	}
+	return r.config.AuthMiddleware
+}
+
 // setupMarketplaceRoutes configure les routes de la marketplace
 func (r *APIRouter) setupMarketplaceRoutes(router *gin.RouterGroup) {
 	uploadDir := r.config.UploadDir
@@ -19,6 +34,12 @@ func (r *APIRouter) setupMarketplaceRoutes(router *gin.RouterGroup) {
 		uploadDir = "uploads/tracks"
 	}
 
+	var marketService marketplace.MarketplaceService
+	var marketServicePtr *marketplace.Service
+	if r.config.MarketplaceServiceOverride != nil {
+		marketService = r.config.MarketplaceServiceOverride.(marketplace.MarketplaceService)
+		marketServicePtr = r.config.MarketplaceServiceOverride.(*marketplace.Service)
+	} else {
 		storageService := services.NewTrackStorageService(uploadDir, false, r.logger)
 		opts := []marketplace.ServiceOption{}
 		if r.config.HyperswitchEnabled && r.config.HyperswitchAPIKey != "" && r.config.HyperswitchURL != "" {
@@ -33,12 +54,20 @@ func (r *APIRouter) setupMarketplaceRoutes(router *gin.RouterGroup) {
 				marketplace.WithHyperswitchConfig(true, r.config.CheckoutSuccessURL),
 			)
 		}
+		if r.config.StripeConnectEnabled && r.config.StripeConnectSecretKey != "" {
+			scs := services.NewStripeConnectService(r.db.GormDB, r.config.StripeConnectSecretKey, r.logger)
+			opts = append(opts, marketplace.WithTransferService(scs, r.config.PlatformFeeRate))
+		}
+		svc := marketplace.NewService(r.db.GormDB, r.logger, storageService, opts...)
+		marketService = svc
+		marketServicePtr = svc
+	}
+
 	var stripeConnectSvc *services.StripeConnectService
 	if r.config.StripeConnectEnabled && r.config.StripeConnectSecretKey != "" {
 		stripeConnectSvc = services.NewStripeConnectService(r.db.GormDB, r.config.StripeConnectSecretKey, r.logger)
-		opts = append(opts, marketplace.WithTransferService(stripeConnectSvc, r.config.PlatformFeeRate))
 	}
-	marketService := marketplace.NewService(r.db.GormDB, r.logger, storageService, opts...)
+
 	productPreviewDir := uploadDir
 	if productPreviewDir == "" {
 		productPreviewDir = "uploads"
@@ -51,13 +80,13 @@ func (r *APIRouter) setupMarketplaceRoutes(router *gin.RouterGroup) {
 	group.GET("/products/:id/preview", marketHandler.StreamProductPreview)
 	group.GET("/products/:id/reviews", marketHandler.ListReviews)
 
-	if r.config.AuthMiddleware != nil {
+	if auth := r.authForMarketplace(); auth != nil {
 		protected := group.Group("")
-		protected.Use(r.config.AuthMiddleware.RequireAuth())
+		protected.Use(auth.RequireAuth())
 		r.applyCSRFProtection(protected)
 
 		createGroup := protected.Group("")
-		createGroup.Use(r.config.AuthMiddleware.RequireContentCreatorRole())
+		createGroup.Use(auth.RequireContentCreatorRole())
 		createGroup.POST("/products", marketHandler.CreateProduct)
 		createGroup.POST("/products/:id/preview", marketHandler.UploadProductPreview)
 
@@ -73,8 +102,8 @@ func (r *APIRouter) setupMarketplaceRoutes(router *gin.RouterGroup) {
 			}
 			return product.SellerID, nil
 		}
-		protected.PUT("/products/:id", r.config.AuthMiddleware.RequireOwnershipOrAdmin("product", productOwnerResolver), marketHandler.UpdateProduct)
-		protected.PUT("/products/:id/images", r.config.AuthMiddleware.RequireOwnershipOrAdmin("product", productOwnerResolver), marketHandler.UpdateProductImages)
+		protected.PUT("/products/:id", auth.RequireOwnershipOrAdmin("product", productOwnerResolver), marketHandler.UpdateProduct)
+		protected.PUT("/products/:id/images", auth.RequireOwnershipOrAdmin("product", productOwnerResolver), marketHandler.UpdateProductImages)
 
 		protected.GET("/orders", marketHandler.ListOrders)
 		protected.GET("/orders/:id", marketHandler.GetOrder)
@@ -85,17 +114,17 @@ func (r *APIRouter) setupMarketplaceRoutes(router *gin.RouterGroup) {
 		protected.GET("/licenses/mine", marketHandler.GetMyLicenses)
 		protected.POST("/products/:id/reviews", marketHandler.CreateReview)
 
-		marketplaceExtHandler := handlers.NewMarketplaceExtHandler(marketService, r.logger)
+		marketplaceExtHandler := handlers.NewMarketplaceExtHandler(marketServicePtr, r.logger)
 		protected.GET("/wishlist", marketplaceExtHandler.GetWishlist)
 		protected.POST("/wishlist", marketplaceExtHandler.AddToWishlist)
 		protected.DELETE("/wishlist/:productId", marketplaceExtHandler.RemoveFromWishlist)
 	}
 
 	sell := router.Group("/sell")
-	if r.config.AuthMiddleware != nil {
+	if auth := r.authForMarketplace(); auth != nil {
 		sellProtected := sell.Group("")
-		sellProtected.Use(r.config.AuthMiddleware.RequireAuth())
-		sellProtected.Use(r.config.AuthMiddleware.RequireContentCreatorRole())
+		sellProtected.Use(auth.RequireAuth())
+		sellProtected.Use(auth.RequireContentCreatorRole())
 		r.applyCSRFProtection(sellProtected)
 		sellProtected.GET("/stats", marketHandler.GetSellStats)
 		sellProtected.GET("/stats/evolution", marketHandler.GetSellStatsEvolution)
@@ -110,12 +139,12 @@ func (r *APIRouter) setupMarketplaceRoutes(router *gin.RouterGroup) {
 	}
 
 	commerce := router.Group("/commerce")
-	if r.config.AuthMiddleware != nil {
+	if auth := r.authForMarketplace(); auth != nil {
 		cartProtected := commerce.Group("")
-		cartProtected.Use(r.config.AuthMiddleware.RequireAuth())
+		cartProtected.Use(auth.RequireAuth())
 		r.applyCSRFProtection(cartProtected)
 
-		marketplaceExtHandler := handlers.NewMarketplaceExtHandler(marketService, r.logger)
+		marketplaceExtHandler := handlers.NewMarketplaceExtHandler(marketServicePtr, r.logger)
 		cartProtected.GET("/cart", marketplaceExtHandler.GetCart)
 		cartProtected.GET("/promo/:code", marketplaceExtHandler.ValidatePromo)
 		cartProtected.POST("/cart/items", marketplaceExtHandler.AddToCart)

veza-backend-api/internal/api/routes_webhooks.go

@@ -85,6 +85,9 @@ func (r *APIRouter) hyperswitchWebhookHandler() gin.HandlerFunc {
 // getMarketplaceService returns the marketplace service with Hyperswitch wiring.
 // Used by webhook handler; mirrors setupMarketplaceRoutes service creation.
 func (r *APIRouter) getMarketplaceService() marketplace.MarketplaceService {
+	if r.config.MarketplaceServiceOverride != nil {
+		return r.config.MarketplaceServiceOverride.(marketplace.MarketplaceService)
+	}
 	uploadDir := r.config.UploadDir
 	if uploadDir == "" {
 		uploadDir = "uploads/tracks"

veza-backend-api/internal/config/config.go

@@ -146,6 +146,12 @@ type Config struct {
 	HyperswitchWebhookSecret string // Webhook signature verification secret
 	CheckoutSuccessURL     string // URL to redirect after successful payment (e.g. /checkout/success)
 
+	// Test-only: when set, used instead of creating marketplace from config (integration tests)
+	MarketplaceServiceOverride interface{}
+
+	// Test-only: when set, used instead of AuthMiddleware (integration tests, e.g. X-User-ID header)
+	AuthMiddlewareOverride interface{}
+
 	// Stripe Connect (Seller Payout v0.602)
 	StripeConnectEnabled       bool   // STRIPE_CONNECT_ENABLED
 	StripeConnectSecretKey     string // STRIPE_SECRET_KEY (for server-side Stripe API calls)

veza-backend-api/tests/integration/payment_flow_test.go

@@ -0,0 +1,270 @@
+//go:build integration
+// +build integration
+
+package integration
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+
+	"veza-backend-api/internal/api"
+	"veza-backend-api/internal/config"
+	"veza-backend-api/internal/core/marketplace"
+	"veza-backend-api/internal/database"
+	"veza-backend-api/internal/metrics"
+	"veza-backend-api/internal/middleware"
+	"veza-backend-api/internal/models"
+	"veza-backend-api/internal/services"
+)
+
+// mockPaymentProvider returns fixed payment_id for CreatePayment (no real Hyperswitch call)
+type mockPaymentProvider struct {
+	paymentID    string
+	clientSecret string
+}
+
+func (m *mockPaymentProvider) CreatePayment(_ context.Context, _ int64, _ string, _ string, _ string, _ map[string]string) (string, string, error) {
+	return m.paymentID, m.clientSecret, nil
+}
+
+func (m *mockPaymentProvider) GetPayment(_ context.Context, _ string) (string, error) {
+	return "succeeded", nil
+}
+
+// mockTransferService records CreateTransfer calls
+type mockTransferService struct {
+	calls []struct {
+		SellerID uuid.UUID
+		Amount   int64
+		Currency string
+		OrderID  string
+	}
+}
+
+func (m *mockTransferService) CreateTransfer(_ context.Context, sellerUserID uuid.UUID, amount int64, currency, orderID string) error {
+	m.calls = append(m.calls, struct {
+		SellerID uuid.UUID
+		Amount   int64
+		Currency string
+		OrderID  string
+	}{sellerUserID, amount, currency, orderID})
+	return nil
+}
+
+// testAuthMiddleware reads X-User-ID header and sets user_id in context (for integration tests)
+type testAuthMiddleware struct{}
+
+func (t *testAuthMiddleware) RequireAuth() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		if userIDStr := c.GetHeader("X-User-ID"); userIDStr != "" {
+			if userID, err := uuid.Parse(userIDStr); err == nil {
+				c.Set("user_id", userID)
+				c.Next()
+				return
+			}
+		}
+		c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "Unauthorized"})
+	}
+}
+
+func (t *testAuthMiddleware) RequireContentCreatorRole() gin.HandlerFunc {
+	return t.RequireAuth()
+}
+
+func (t *testAuthMiddleware) RequireOwnershipOrAdmin(_ string, _ middleware.ResourceOwnerResolver) gin.HandlerFunc {
+	return t.RequireAuth()
+}
+
+func (t *testAuthMiddleware) RequirePermission(_ string) gin.HandlerFunc {
+	return t.RequireAuth()
+}
+
+func (t *testAuthMiddleware) RequireAdmin() gin.HandlerFunc {
+	return t.RequireAuth()
+}
+
+func (t *testAuthMiddleware) OptionalAuth() gin.HandlerFunc {
+	return func(c *gin.Context) { c.Next() }
+}
+
+func (t *testAuthMiddleware) RefreshToken() gin.HandlerFunc {
+	return func(c *gin.Context) { c.AbortWithStatus(http.StatusNotImplemented) }
+}
+
+func setupPaymentFlowRouter(t *testing.T, db *gorm.DB, marketService *marketplace.Service) *gin.Engine {
+	t.Helper()
+	os.Setenv("ENABLE_CLAMAV", "false")
+	os.Setenv("CLAMAV_REQUIRED", "false")
+
+	gin.SetMode(gin.TestMode)
+	router := gin.New()
+
+	sqlDB, err := db.DB()
+	require.NoError(t, err)
+
+	vezaDB := &database.Database{
+		DB:     sqlDB,
+		GormDB: db,
+		Logger: zap.NewNop(),
+	}
+
+	cfg := &config.Config{
+		HyperswitchWebhookSecret:   "test-secret-at-least-32-chars-long",
+		JWTSecret:                 "test-jwt-secret-key-minimum-32-characters-long",
+		JWTIssuer:                 "veza-api",
+		JWTAudience:               "veza-app",
+		Logger:                    zap.NewNop(),
+		RedisClient:               nil,
+		ErrorMetrics:              metrics.NewErrorMetrics(),
+		UploadDir:                 "uploads/test",
+		Env:                       "development",
+		Database:                  vezaDB,
+		CORSOrigins:               []string{"*"},
+		HandlerTimeout:            30 * time.Second,
+		RateLimitLimit:            100,
+		RateLimitWindow:           60,
+		AuthRateLimitLoginAttempts: 10,
+		AuthRateLimitLoginWindow:  15,
+		MarketplaceServiceOverride: marketService,
+	}
+	require.NoError(t, cfg.InitServicesForTest())
+	require.NoError(t, cfg.InitMiddlewaresForTest())
+	cfg.AuthMiddlewareOverride = &testAuthMiddleware{}
+
+	apiRouter := api.NewAPIRouter(vezaDB, cfg)
+	require.NoError(t, apiRouter.Setup(router))
+	return router
+}
+
+// TestPaymentFlow_E2E_CartCheckoutWebhook verifies the full payment flow:
+// add to cart -> checkout -> webhook payment_succeeded -> order completed, license created, transfer initiated
+func TestPaymentFlow_E2E_CartCheckoutWebhook(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	require.NoError(t, err)
+	require.NoError(t, db.AutoMigrate(
+		&models.User{},
+		&models.Track{},
+		&marketplace.Product{},
+		&marketplace.Order{},
+		&marketplace.OrderItem{},
+		&marketplace.License{},
+		&marketplace.SellerTransfer{},
+	))
+	// CartItem uses gen_random_uuid() (PostgreSQL) - create manually for SQLite
+	require.NoError(t, db.Exec(`
+		CREATE TABLE IF NOT EXISTS cart_items (
+			id TEXT PRIMARY KEY,
+			user_id TEXT NOT NULL,
+			product_id TEXT NOT NULL,
+			quantity INTEGER DEFAULT 1,
+			created_at DATETIME,
+			updated_at DATETIME
+		)
+	`).Error)
+	db.Callback().Create().Before("gorm:create").Register("generate_uuid_cart_item", func(d *gorm.DB) {
+		if item, ok := d.Statement.Dest.(*marketplace.CartItem); ok && item.ID == uuid.Nil {
+			item.ID = uuid.New()
+		}
+	})
+
+	buyerID := uuid.New()
+	sellerID := uuid.New()
+	trackID := uuid.New()
+
+	require.NoError(t, db.Create(&models.User{ID: buyerID}).Error)
+	require.NoError(t, db.Create(&models.User{ID: sellerID}).Error)
+	require.NoError(t, db.Create(&models.Track{ID: trackID, UserID: sellerID, FilePath: "/test.mp3"}).Error)
+
+	product := &marketplace.Product{
+		ID:          uuid.New(),
+		SellerID:    sellerID,
+		Title:       "Test Product",
+		Price:       9.99,
+		ProductType: "track",
+		TrackID:     &trackID,
+		Status:      marketplace.ProductStatusActive,
+	}
+	require.NoError(t, db.Create(product).Error)
+
+	mockPay := &mockPaymentProvider{paymentID: "pay_mock_123", clientSecret: "pi_secret_xxx"}
+	mockTransfer := &mockTransferService{}
+	storageService := services.NewTrackStorageService("uploads/test", false, zap.NewNop())
+	marketService := marketplace.NewService(db, zap.NewNop(), storageService,
+		marketplace.WithPaymentProvider(mockPay),
+		marketplace.WithHyperswitchConfig(true, "/purchases"),
+		marketplace.WithTransferService(mockTransfer, 0.10),
+	)
+
+	router := setupPaymentFlowRouter(t, db, marketService)
+
+	// Step 1: Add to cart
+	addCartBody, _ := json.Marshal(map[string]interface{}{
+		"product_id": product.ID.String(),
+		"quantity":   1,
+	})
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/commerce/cart/items", bytes.NewReader(addCartBody))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("X-User-ID", buyerID.String())
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+	require.Equal(t, http.StatusCreated, w.Code, "add to cart must succeed: %s", w.Body.String())
+
+	// Step 2: Checkout
+	req = httptest.NewRequest(http.MethodPost, "/api/v1/commerce/cart/checkout", bytes.NewReader([]byte("{}")))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("X-User-ID", buyerID.String())
+	w = httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+	require.Equal(t, http.StatusCreated, w.Code, "checkout must succeed: %s", w.Body.String())
+
+	var checkoutResp map[string]interface{}
+	require.NoError(t, json.Unmarshal(w.Body.Bytes(), &checkoutResp))
+	data, ok := checkoutResp["data"].(map[string]interface{})
+	require.True(t, ok)
+	orderData, ok := data["order"].(map[string]interface{})
+	require.True(t, ok)
+	orderIDStr, ok := orderData["id"].(string)
+	require.True(t, ok)
+	assert.NotEmpty(t, data["client_secret"], "client_secret must be present")
+	assert.Equal(t, "pay_mock_123", data["payment_id"], "payment_id must match mock")
+
+	// Step 3: Simulate webhook payment_succeeded
+	payload, _ := json.Marshal(map[string]string{
+		"payment_id": "pay_mock_123",
+		"status":     "succeeded",
+	})
+	signature := computeWebhookSignature(payload, "test-secret-at-least-32-chars-long")
+	req = httptest.NewRequest(http.MethodPost, "/api/v1/webhooks/hyperswitch", bytes.NewReader(payload))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("x-webhook-signature-512", signature)
+	w = httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+	assert.Equal(t, http.StatusOK, w.Code, "webhook must succeed: %s", w.Body.String())
+
+	// Assertions: order completed, license created, transfer initiated
+	orderID, _ := uuid.Parse(orderIDStr)
+	var order marketplace.Order
+	require.NoError(t, db.First(&order, orderID).Error)
+	assert.Equal(t, "completed", order.Status)
+
+	var licenses []marketplace.License
+	require.NoError(t, db.Where("order_id = ?", orderID).Find(&licenses).Error)
+	assert.Len(t, licenses, 1, "must have 1 license")
+
+	assert.Len(t, mockTransfer.calls, 1, "transfer must be initiated")
+	assert.Equal(t, sellerID, mockTransfer.calls[0].SellerID)
+}

veza-backend-api/tests/integration/refund_flow_test.go

@@ -0,0 +1,174 @@
+//go:build integration
+// +build integration
+
+package integration
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+
+	"veza-backend-api/internal/api"
+	"veza-backend-api/internal/config"
+	"veza-backend-api/internal/core/marketplace"
+	"veza-backend-api/internal/database"
+	"veza-backend-api/internal/metrics"
+	"veza-backend-api/internal/models"
+	"veza-backend-api/internal/services"
+)
+
+// mockRefundPaymentProvider implements PaymentProvider and Refund for refund flow test
+type mockRefundPaymentProvider struct {
+	refundErr error
+}
+
+func (m *mockRefundPaymentProvider) CreatePayment(_ context.Context, _ int64, _ string, _ string, _ string, _ map[string]string) (string, string, error) {
+	return "pay_refund_mock", "secret", nil
+}
+
+func (m *mockRefundPaymentProvider) GetPayment(_ context.Context, _ string) (string, error) {
+	return "succeeded", nil
+}
+
+func (m *mockRefundPaymentProvider) Refund(_ context.Context, _ string, _ *int64, _ string) error {
+	return m.refundErr
+}
+
+func setupRefundFlowRouter(t *testing.T, db *gorm.DB, marketService *marketplace.Service) *gin.Engine {
+	t.Helper()
+	os.Setenv("ENABLE_CLAMAV", "false")
+	os.Setenv("CLAMAV_REQUIRED", "false")
+
+	gin.SetMode(gin.TestMode)
+	router := gin.New()
+
+	sqlDB, err := db.DB()
+	require.NoError(t, err)
+
+	vezaDB := &database.Database{
+		DB:     sqlDB,
+		GormDB: db,
+		Logger: zap.NewNop(),
+	}
+
+	cfg := &config.Config{
+		HyperswitchWebhookSecret:   "test-secret",
+		JWTSecret:                 "test-jwt-secret-key-minimum-32-characters-long",
+		JWTIssuer:                 "veza-api",
+		JWTAudience:               "veza-app",
+		Logger:                    zap.NewNop(),
+		RedisClient:               nil,
+		ErrorMetrics:              metrics.NewErrorMetrics(),
+		UploadDir:                 "uploads/test",
+		Env:                       "development",
+		Database:                  vezaDB,
+		CORSOrigins:               []string{"*"},
+		HandlerTimeout:            30 * time.Second,
+		RateLimitLimit:            100,
+		RateLimitWindow:           60,
+		AuthRateLimitLoginAttempts: 10,
+		AuthRateLimitLoginWindow:  15,
+		MarketplaceServiceOverride: marketService,
+		AuthMiddlewareOverride:    &testAuthMiddleware{},
+	}
+	require.NoError(t, cfg.InitServicesForTest())
+	require.NoError(t, cfg.InitMiddlewaresForTest())
+
+	apiRouter := api.NewAPIRouter(vezaDB, cfg)
+	require.NoError(t, apiRouter.Setup(router))
+	return router
+}
+
+// TestRefundFlow_CompletedOrder_Refund_RevokesLicense verifies: order completed -> refund request ->
+// order status refunded, licence revoked.
+func TestRefundFlow_CompletedOrder_Refund_RevokesLicense(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	require.NoError(t, err)
+	require.NoError(t, db.AutoMigrate(
+		&models.User{},
+		&models.Track{},
+		&marketplace.Product{},
+		&marketplace.Order{},
+		&marketplace.OrderItem{},
+		&marketplace.License{},
+		&marketplace.SellerTransfer{},
+	))
+
+	buyerID := uuid.New()
+	sellerID := uuid.New()
+	trackID := uuid.New()
+	productID := uuid.New()
+	orderID := uuid.New()
+
+	require.NoError(t, db.Create(&models.User{ID: buyerID}).Error)
+	require.NoError(t, db.Create(&models.User{ID: sellerID}).Error)
+	require.NoError(t, db.Create(&models.Track{ID: trackID, UserID: sellerID, FilePath: "/t.mp3"}).Error)
+	require.NoError(t, db.Create(&marketplace.Product{
+		ID:          productID,
+		SellerID:    sellerID,
+		Title:       "Test Product",
+		Price:       9.99,
+		ProductType: "track",
+		TrackID:     &trackID,
+		Status:      marketplace.ProductStatusActive,
+	}).Error)
+	require.NoError(t, db.Create(&marketplace.Order{
+		ID:                   orderID,
+		BuyerID:              buyerID,
+		TotalAmount:          9.99,
+		Currency:             "EUR",
+		Status:               "completed",
+		HyperswitchPaymentID: "pay_refund_mock",
+	}).Error)
+	require.NoError(t, db.Create(&marketplace.OrderItem{
+		ID:        uuid.New(),
+		OrderID:   orderID,
+		ProductID: productID,
+		Price:     9.99,
+	}).Error)
+	require.NoError(t, db.Create(&marketplace.License{
+		ID:        uuid.New(),
+		BuyerID:   buyerID,
+		TrackID:   trackID,
+		ProductID: productID,
+		OrderID:   orderID,
+		Type:      marketplace.LicenseBasic,
+	}).Error)
+
+	mockPay := &mockRefundPaymentProvider{}
+	storageService := services.NewTrackStorageService("uploads/test", false, zap.NewNop())
+	marketService := marketplace.NewService(db, zap.NewNop(), storageService, marketplace.WithPaymentProvider(mockPay))
+
+	router := setupRefundFlowRouter(t, db, marketService)
+
+	body, _ := json.Marshal(map[string]string{"reason": "Customer request"})
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/marketplace/orders/"+orderID.String()+"/refund", bytes.NewReader(body))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("X-User-ID", buyerID.String())
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusOK, w.Code, "refund must succeed: %s", w.Body.String())
+
+	var order marketplace.Order
+	require.NoError(t, db.First(&order, orderID).Error)
+	assert.Equal(t, "refunded", order.Status)
+
+	var licenses []marketplace.License
+	require.NoError(t, db.Where("order_id = ?", orderID).Find(&licenses).Error)
+	require.Len(t, licenses, 1)
+	assert.NotNil(t, licenses[0].RevokedAt, "license must be revoked")
+}

veza-backend-api/tests/integration/webhook_idempotency_test.go

@@ -0,0 +1,157 @@
+//go:build integration
+// +build integration
+
+package integration
+
+import (
+	"bytes"
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+
+	"veza-backend-api/internal/api"
+	"veza-backend-api/internal/config"
+	"veza-backend-api/internal/core/marketplace"
+	"veza-backend-api/internal/database"
+	"veza-backend-api/internal/metrics"
+	"veza-backend-api/internal/models"
+	"veza-backend-api/internal/services"
+)
+
+func setupWebhookIdempotencyRouter(t *testing.T, db *gorm.DB, marketService *marketplace.Service) *gin.Engine {
+	t.Helper()
+	os.Setenv("ENABLE_CLAMAV", "false")
+	os.Setenv("CLAMAV_REQUIRED", "false")
+
+	gin.SetMode(gin.TestMode)
+	router := gin.New()
+
+	sqlDB, err := db.DB()
+	require.NoError(t, err)
+
+	vezaDB := &database.Database{
+		DB:     sqlDB,
+		GormDB: db,
+		Logger: zap.NewNop(),
+	}
+
+	cfg := &config.Config{
+		HyperswitchWebhookSecret:   "test-secret-at-least-32-chars-long",
+		JWTSecret:                 "test-jwt-secret-key-minimum-32-characters-long",
+		JWTIssuer:                 "veza-api",
+		JWTAudience:               "veza-app",
+		Logger:                    zap.NewNop(),
+		RedisClient:               nil,
+		ErrorMetrics:              metrics.NewErrorMetrics(),
+		UploadDir:                 "uploads/test",
+		Env:                       "development",
+		Database:                  vezaDB,
+		CORSOrigins:               []string{"*"},
+		HandlerTimeout:            30 * time.Second,
+		RateLimitLimit:            100,
+		RateLimitWindow:           60,
+		AuthRateLimitLoginAttempts: 10,
+		AuthRateLimitLoginWindow:  15,
+		MarketplaceServiceOverride: marketService,
+	}
+	require.NoError(t, cfg.InitServicesForTest())
+	require.NoError(t, cfg.InitMiddlewaresForTest())
+
+	apiRouter := api.NewAPIRouter(vezaDB, cfg)
+	require.NoError(t, apiRouter.Setup(router))
+	return router
+}
+
+// TestWebhookIdempotency_ThreeIdenticalWebhooks_CreatesOneOrder verifies that sending
+// the same payment_succeeded webhook 3 times results in 1 completed order and 1 license.
+func TestWebhookIdempotency_ThreeIdenticalWebhooks_CreatesOneOrder(t *testing.T) {
+	db, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	require.NoError(t, err)
+	// Ensure single connection for sqlite :memory: (each new connection gets empty DB)
+	sqlDB, _ := db.DB()
+	sqlDB.SetMaxOpenConns(1)
+	require.NoError(t, db.AutoMigrate(
+		&models.User{},
+		&models.Track{},
+		&marketplace.Product{},
+		&marketplace.Order{},
+		&marketplace.OrderItem{},
+		&marketplace.License{},
+		&marketplace.SellerTransfer{},
+	))
+
+	buyerID := uuid.New()
+	sellerID := uuid.New()
+	trackID := uuid.New()
+
+	require.NoError(t, db.Create(&models.User{ID: buyerID}).Error)
+	require.NoError(t, db.Create(&models.User{ID: sellerID}).Error)
+	require.NoError(t, db.Create(&models.Track{ID: trackID, UserID: sellerID, FilePath: "/test.mp3"}).Error)
+
+	product := &marketplace.Product{
+		ID:          uuid.New(),
+		SellerID:    sellerID,
+		Title:       "Test Product",
+		Price:       9.99,
+		ProductType: "track",
+		TrackID:     &trackID,
+		Status:      marketplace.ProductStatusActive,
+	}
+	require.NoError(t, db.Create(product).Error)
+
+	order := &marketplace.Order{
+		ID:                   uuid.New(),
+		BuyerID:              buyerID,
+		TotalAmount:          9.99,
+		Currency:             "EUR",
+		Status:               "pending",
+		HyperswitchPaymentID: "pay_idem_123",
+	}
+	require.NoError(t, db.Create(order).Error)
+	require.NoError(t, db.Create(&marketplace.OrderItem{
+		ID:        uuid.New(),
+		OrderID:   order.ID,
+		ProductID: product.ID,
+		Price:     9.99,
+	}).Error)
+
+	storageService := services.NewTrackStorageService("uploads/test", false, zap.NewNop())
+	marketService := marketplace.NewService(db, zap.NewNop(), storageService)
+
+	router := setupWebhookIdempotencyRouter(t, db, marketService)
+
+	payload, _ := json.Marshal(map[string]string{
+		"payment_id": "pay_idem_123",
+		"status":     "succeeded",
+	})
+	signature := computeWebhookSignature(payload, "test-secret-at-least-32-chars-long")
+
+	for i := 0; i < 3; i++ {
+		req := httptest.NewRequest(http.MethodPost, "/api/v1/webhooks/hyperswitch", bytes.NewReader(payload))
+		req.Header.Set("Content-Type", "application/json")
+		req.Header.Set("x-webhook-signature-512", signature)
+		w := httptest.NewRecorder()
+		router.ServeHTTP(w, req)
+		assert.Equal(t, http.StatusOK, w.Code, "webhook call %d must return 200", i+1)
+	}
+
+	var orders []marketplace.Order
+	require.NoError(t, db.Where("hyperswitch_payment_id = ?", "pay_idem_123").Find(&orders).Error)
+	assert.Len(t, orders, 1, "must have exactly 1 order")
+	assert.Equal(t, "completed", orders[0].Status, "order must be completed")
+
+	var licenses []marketplace.License
+	require.NoError(t, db.Where("order_id = ?", order.ID).Find(&licenses).Error)
+	assert.Len(t, licenses, 1, "must have exactly 1 license")
+}

veza-backend-api/tests/integration/webhook_security_test.go

@@ -0,0 +1,126 @@
+//go:build integration
+// +build integration
+
+package integration
+
+import (
+	"bytes"
+	"net/http"
+	"net/http/httptest"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+	"go.uber.org/zap"
+	"gorm.io/driver/sqlite"
+	"gorm.io/gorm"
+
+	"veza-backend-api/internal/api"
+	"veza-backend-api/internal/config"
+	"veza-backend-api/internal/core/marketplace"
+	"veza-backend-api/internal/database"
+	"veza-backend-api/internal/metrics"
+	"veza-backend-api/internal/models"
+)
+
+func setupWebhookSecurityRouter(t *testing.T, webhookSecret string) *gin.Engine {
+	t.Helper()
+	os.Setenv("ENABLE_CLAMAV", "false")
+	os.Setenv("CLAMAV_REQUIRED", "false")
+
+	gin.SetMode(gin.TestMode)
+	router := gin.New()
+
+	gormDB, err := gorm.Open(sqlite.Open(":memory:"), &gorm.Config{})
+	require.NoError(t, err)
+	require.NoError(t, gormDB.AutoMigrate(
+		&models.User{},
+		&models.Track{},
+		&marketplace.Product{},
+		&marketplace.Order{},
+		&marketplace.OrderItem{},
+		&marketplace.License{},
+		&marketplace.SellerTransfer{},
+	))
+	sqlDB, err := gormDB.DB()
+	require.NoError(t, err)
+
+	vezaDB := &database.Database{
+		DB:     sqlDB,
+		GormDB: gormDB,
+		Logger: zap.NewNop(),
+	}
+
+	cfg := &config.Config{
+		HyperswitchWebhookSecret:  webhookSecret,
+		JWTSecret:                "test-jwt-secret-key-minimum-32-characters-long",
+		JWTIssuer:                "veza-api",
+		JWTAudience:              "veza-app",
+		Logger:                   zap.NewNop(),
+		RedisClient:              nil,
+		ErrorMetrics:             metrics.NewErrorMetrics(),
+		UploadDir:                "uploads/test",
+		Env:                      "development",
+		Database:                 vezaDB,
+		CORSOrigins:              []string{"*"},
+		HandlerTimeout:            30 * time.Second,
+		RateLimitLimit:           100,
+		RateLimitWindow:          60,
+		AuthRateLimitLoginAttempts: 10,
+		AuthRateLimitLoginWindow: 15,
+	}
+	require.NoError(t, cfg.InitServicesForTest())
+	require.NoError(t, cfg.InitMiddlewaresForTest())
+
+	apiRouter := api.NewAPIRouter(vezaDB, cfg)
+	require.NoError(t, apiRouter.Setup(router))
+	return router
+}
+
+// TestWebhookSecurity_EmptySecret_Returns500 verifies that when HyperswitchWebhookSecret
+// is empty, the webhook handler returns 500 (VEZA-SEC-005).
+func TestWebhookSecurity_EmptySecret_Returns500(t *testing.T) {
+	router := setupWebhookSecurityRouter(t, "")
+
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/webhooks/hyperswitch", bytes.NewReader([]byte(`{"test": true}`)))
+	req.Header.Set("Content-Type", "application/json")
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusInternalServerError, w.Code, "empty webhook secret must return 500")
+}
+
+// TestWebhookSecurity_InvalidSignature_Returns401 verifies that with a configured secret,
+// invalid or missing signature returns 401.
+func TestWebhookSecurity_InvalidSignature_Returns401(t *testing.T) {
+	router := setupWebhookSecurityRouter(t, "test-secret-at-least-32-chars-long")
+
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/webhooks/hyperswitch", bytes.NewReader([]byte(`{"payment_id":"pay_123","status":"succeeded"}`)))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("x-webhook-signature-512", "invalid_signature")
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusUnauthorized, w.Code, "invalid signature must return 401")
+}
+
+// TestWebhookSecurity_ValidSignature_Returns200 verifies that with a configured secret
+// and valid HMAC-SHA512 signature, the webhook returns 200.
+func TestWebhookSecurity_ValidSignature_Returns200(t *testing.T) {
+	secret := "test-secret-at-least-32-chars-long"
+	payload := []byte(`{"payment_id":"pay_nonexistent","status":"succeeded"}`)
+	signature := computeWebhookSignature(payload, secret)
+
+	router := setupWebhookSecurityRouter(t, secret)
+
+	req := httptest.NewRequest(http.MethodPost, "/api/v1/webhooks/hyperswitch", bytes.NewReader(payload))
+	req.Header.Set("Content-Type", "application/json")
+	req.Header.Set("x-webhook-signature-512", signature)
+	w := httptest.NewRecorder()
+	router.ServeHTTP(w, req)
+
+	assert.Equal(t, http.StatusOK, w.Code, "valid signature must return 200")
+}

veza-backend-api/tests/integration/webhook_test_helpers.go

@@ -0,0 +1,17 @@
+//go:build integration
+// +build integration
+
+package integration
+
+import (
+	"crypto/hmac"
+	"crypto/sha512"
+	"encoding/hex"
+)
+
+// computeWebhookSignature computes HMAC-SHA512 signature for Hyperswitch webhook payload.
+func computeWebhookSignature(payload []byte, secret string) string {
+	mac := hmac.New(sha512.New, []byte(secret))
+	mac.Write(payload)
+	return hex.EncodeToString(mac.Sum(nil))
+}