add testing/pgruntime

Testing pgruntime has quickly turned out to be a nightmare, because so
many parts of the test logic are not easily reproducible (e.g.
`stopDBIfLingering`). I decided to not waste a bunch of time testing
code that is relatively compact and easy to verify by careful
examination, and that is unlikely to change a lot in the future.

1 files changed, 47 insertions, 0 deletions

diff --git a/testing/pgruntime/helpers_test.go b/testing/pgruntime/helpers_test.go
new file mode 100644
index 0000000..ca4ffd2
--- /dev/null
+++ b/testing/pgruntime/helpers_test.go
@@ -0,0 +1,47 @@
+// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
+// SPDX-License-Identifier: Apache-2.0
+
+package pgruntime_test
+
+import (
+	"context"
+	"database/sql"
+
+	"go.xyrillian.de/gg/errext"
+	"go.xyrillian.de/gg/gsql"
+)
+
+// Convenience function for executing a one-off SQL query returning no rows.
+// TODO: move to gsql
+func execQuery(ctx context.Context, db gsql.Handle, query string, args []any) (sql.Result, error) {
+	stmt, err := db.GSQLPrepare(ctx, query, false)
+	if err != nil {
+		return nil, err
+	}
+	result, err := stmt.Exec(ctx, args)
+	return result, errext.WithCleanup(err, "stmt.Close", stmt.Close())
+}
+
+// Convenience function for executing a one-off SQL query returning one row.
+func queryRow(ctx context.Context, db gsql.Handle, query string, args, slots []any) error {
+	stmt, err := db.GSQLPrepare(ctx, query, false)
+	if err != nil {
+		return err
+	}
+	err = stmt.QueryRow(ctx, args, slots)
+	return errext.WithCleanup(err, "stmt.Close", stmt.Close())
+}
+
+// Convenience function for executing a one-off SQL query returning one value.
+// TODO: move to gsql
+func selectOneValue[T any](ctx context.Context, db gsql.Handle, query string, args ...any) (T, error) {
+	stmt, err := db.GSQLPrepare(ctx, query, false)
+	if err != nil {
+		var none T
+		return none, err
+	}
+
+	var result T
+	err = stmt.QueryRow(ctx, args, []any{&result})
+	return result, errext.WithCleanup(err, "stmt.Close", stmt.Close())
+}