refactor(tests): centralize DB query assertions with helpers

Reduce repetitive raw SQL in test bodies by routing scalar and multi-column checks through shared helpers, keeping test intent clearer without changing behavior.

go-backend/tests/contract/db_test_helper_internal_test.go

@@ -0,0 +1,19 @@
+package contract
+
+import (
+	"testing"
+
+	"go-backend/internal/store/repo"
+)
+
+func mustLastInsertID(t *testing.T, r *repo.Repository, label string) int64 {
+	t.Helper()
+	var id int64
+	if err := r.DB().Raw("SELECT last_insert_rowid()").Row().Scan(&id); err != nil {
+		t.Fatalf("read last_insert_rowid for %s: %v", label, err)
+	}
+	if id <= 0 {
+		t.Fatalf("invalid last_insert_rowid for %s: %d", label, id)
+	}
+	return id
+}