diff --git a/apps/backend/internal/registration/service_integration_test.go b/apps/backend/internal/registration/service_integration_test.go
new file mode 100644
index 0000000..679ee6f
--- /dev/null
+++ b/apps/backend/internal/registration/service_integration_test.go
@@ -0,0 +1,153 @@
+//go:build integration
+
+package registration
+
+import (
+	"context"
+	"fmt"
+	"os"
+	"testing"
+	"time"
+
+	"github.com/get-drexa/drexa/internal/account"
+	"github.com/get-drexa/drexa/internal/blob"
+	"github.com/get-drexa/drexa/internal/database"
+	"github.com/get-drexa/drexa/internal/drive"
+	"github.com/get-drexa/drexa/internal/organization"
+	"github.com/get-drexa/drexa/internal/user"
+	"github.com/get-drexa/drexa/internal/virtualfs"
+	"github.com/testcontainers/testcontainers-go/modules/postgres"
+)
+
+func TestService_Register(t *testing.T) {
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
+	defer cancel()
+
+	pg, err := runPostgres(ctx)
+	if err != nil {
+		t.Skipf("postgres testcontainer unavailable (docker not running/configured?): %v", err)
+	}
+	t.Cleanup(func() { _ = pg.Terminate(ctx) })
+
+	postgresURL, err := pg.ConnectionString(ctx, "sslmode=disable")
+	if err != nil {
+		t.Fatalf("postgres connection string: %v", err)
+	}
+
+	db := database.NewFromPostgres(postgresURL)
+	t.Cleanup(func() { _ = db.Close() })
+
+	if err := database.RunMigrations(ctx, db); err != nil {
+		t.Fatalf("RunMigrations: %v", err)
+	}
+
+	blobRoot, err := os.MkdirTemp("", "drexa-blobs-*")
+	if err != nil {
+		t.Fatalf("temp blob dir: %v", err)
+	}
+	t.Cleanup(func() { _ = os.RemoveAll(blobRoot) })
+
+	blobStore := blob.NewFSStore(blob.FSStoreConfig{Root: blobRoot})
+	if err := blobStore.Initialize(ctx); err != nil {
+		t.Fatalf("blob store init: %v", err)
+	}
+
+	vfs, err := virtualfs.New(blobStore, virtualfs.NewFlatKeyResolver())
+	if err != nil {
+		t.Fatalf("virtualfs.New: %v", err)
+	}
+
+	userSvc := user.NewService()
+	orgSvc := organization.NewService()
+	accSvc := account.NewService()
+	driveSvc := drive.NewService()
+
+	regSvc := NewService(userSvc, orgSvc, accSvc, driveSvc, vfs)
+
+	result, err := regSvc.Register(ctx, db, RegisterOptions{
+		Email:       "reg@example.com",
+		Password:    "password123",
+		DisplayName: "Reg User",
+	})
+	if err != nil {
+		t.Fatalf("Register: %v", err)
+	}
+	if result.User == nil || result.Account == nil || result.Drive == nil {
+		t.Fatalf("expected user, account, and drive to be set")
+	}
+
+	gotUser, err := userSvc.UserByEmail(ctx, db, result.User.Email)
+	if err != nil {
+		t.Fatalf("UserByEmail: %v", err)
+	}
+	if gotUser.ID != result.User.ID {
+		t.Fatalf("unexpected user id: got %q want %q", gotUser.ID, result.User.ID)
+	}
+
+	gotOrg, err := orgSvc.OrganizationByID(ctx, db, result.Account.OrgID)
+	if err != nil {
+		t.Fatalf("OrganizationByID: %v", err)
+	}
+	if gotOrg.Kind != organization.KindPersonal {
+		t.Fatalf("unexpected org kind: got %q want %q", gotOrg.Kind, organization.KindPersonal)
+	}
+	if gotOrg.Name != "Personal" {
+		t.Fatalf("unexpected org name: got %q want %q", gotOrg.Name, "Personal")
+	}
+
+	gotAccount, err := accSvc.AccountByID(ctx, db, gotUser.ID, result.Account.ID)
+	if err != nil {
+		t.Fatalf("AccountByID: %v", err)
+	}
+	if gotAccount.OrgID != gotOrg.ID {
+		t.Fatalf("unexpected account org: got %q want %q", gotAccount.OrgID, gotOrg.ID)
+	}
+	if gotAccount.UserID != gotUser.ID {
+		t.Fatalf("unexpected account user: got %q want %q", gotAccount.UserID, gotUser.ID)
+	}
+	if gotAccount.Role != account.RoleAdmin {
+		t.Fatalf("unexpected account role: got %q want %q", gotAccount.Role, account.RoleAdmin)
+	}
+	if gotAccount.Status != account.StatusActive {
+		t.Fatalf("unexpected account status: got %q want %q", gotAccount.Status, account.StatusActive)
+	}
+
+	gotDrive, err := driveSvc.DriveByID(ctx, db, result.Drive.ID)
+	if err != nil {
+		t.Fatalf("DriveByID: %v", err)
+	}
+	if gotDrive.OrgID != gotOrg.ID {
+		t.Fatalf("unexpected drive org: got %q want %q", gotDrive.OrgID, gotOrg.ID)
+	}
+	if gotDrive.OwnerAccountID == nil || *gotDrive.OwnerAccountID != gotAccount.ID {
+		t.Fatalf("unexpected drive owner account: got %v want %v", gotDrive.OwnerAccountID, gotAccount.ID)
+	}
+
+	root, err := vfs.FindRootDirectory(ctx, db, gotDrive.ID)
+	if err != nil {
+		t.Fatalf("FindRootDirectory: %v", err)
+	}
+	if root.Name != virtualfs.RootDirectoryName {
+		t.Fatalf("unexpected root name: got %q want %q", root.Name, virtualfs.RootDirectoryName)
+	}
+	if root.Kind != virtualfs.NodeKindDirectory {
+		t.Fatalf("unexpected root kind: got %q want %q", root.Kind, virtualfs.NodeKindDirectory)
+	}
+}
+
+func runPostgres(ctx context.Context) (_ *postgres.PostgresContainer, err error) {
+	defer func() {
+		if r := recover(); r != nil {
+			err = fmt.Errorf("testcontainers panic: %v", r)
+		}
+	}()
+
+	return postgres.Run(
+		ctx,
+		"postgres:16-alpine",
+		postgres.WithDatabase("drexa"),
+		postgres.WithUsername("drexa"),
+		postgres.WithPassword("drexa"),
+		postgres.BasicWaitStrategies(),
+	)
+}