this._checkForErrors(responses);
                        this._checkForConnectedDriver();
                    });
            },

            /**
             * Attempts to disconnect the selected Driver from all Instances in the
             * selected Cluster.
             */
            _disconnectDriver() {
                const requests = this.instances.map(instanceHost =>
                    fetch(`//${instanceHost}/REST/ndbench/driver/shutdownclient`));

                Promise.all(requests)
        