Due to the rapid development of open source based Cloud management platforms such as OpenStack, many and various individuals and institutions are trying to construct Cloud computing systems based on open source software projects. It is essential, for those who install, administrate or operate a Cloud, to validate the integrity of the constructed Cloud system. This paper, therefore, proposes the design of a testing tool for validating the integrity of a constructed OpenStack-based Cloud system. Especially, the proposed testing tool utilizes the Tempest project which is an open source project that consists of OpenStack test cases. The proposed testing tool is expected to help developing Cloud technology and Cloud users.