test(tx): regression tests for per-request transactions across all specs

pkg/common/adapters/database/pgsql_preload_test.go

@@ -5,6 +5,7 @@ import (
 	"errors"
 	"strings"
 	"testing"
+	"time"
 
 	"github.com/DATA-DOG/go-sqlmock"
 
@@ -54,3 +55,35 @@ func TestSubqueryPreloadErrorIsReturned(t *testing.T) {
 		})
 	}
 }
+
+// With a single pooled connection, a preload that escaped the transaction would
+// block on the pool and fail on the context timeout.
+func TestSubqueryPreloadRunsOnTheTransaction(t *testing.T) {
+	db, mock, err := sqlmock.New()
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer db.Close()
+	db.SetMaxOpenConns(1)
+
+	mock.ExpectBegin()
+	mock.ExpectQuery(`FROM parents`).WillReturnRows(sqlmock.NewRows([]string{"id"}).AddRow(1))
+	mock.ExpectQuery(`FROM children`).WillReturnRows(sqlmock.NewRows([]string{"id", "user_id"}).AddRow(10, 1))
+	mock.ExpectCommit()
+
+	ctx, cancel := context.WithTimeout(context.Background(), 2*time.Second)
+	defer cancel()
+	var parents []preloadParent
+	err = NewPgSQLAdapter(db).RunInTransaction(ctx, func(tx common.Database) error {
+		return tx.NewSelect().Model(&preloadParent{}).PreloadRelation("Children").Scan(ctx, &parents)
+	})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if err := mock.ExpectationsWereMet(); err != nil {
+		t.Fatal(err)
+	}
+	if len(parents) != 1 || len(parents[0].Children) != 1 {
+		t.Fatalf("preloaded children missing: %+v", parents)
+	}
+}