Comment 2 for bug 1578137

In case user has access to UI, changed credentials can be supplied directly through "Provide credentials" drop-down form. But as correctly described here - fuel client does not support the possibility to provide new credentials to OSTF adapter.

The credentials data must be send in payload of request for test run start in 'ostf_os_access_creds' field. The access data must have following format:
{ostf_os_username: username, ostf_os_tenant_name: tenant_name, ostf_os_password: password}