Method begin_nested

src/database/mock.rs:377–383

(&mut self, db_backend: DbBackend)

    }

    fn begin_nested(&mut self, db_backend: DbBackend) {
        self.transaction_depth += 1;
        self.push(Statement::from_string(
            db_backend,
            format!("SAVEPOINT savepoint_{}", self.transaction_depth),
        ));
    }

    fn commit(&mut self, db_backend: DbBackend) -> bool {
        if self.transaction_depth == 0 {