For more information as guidelines for summative evaluation, please refer here. Some of the discuss articles are:

• 5 keys to a successful usability test
• 8 guidelines for usability testing
• 90% of all usability testing is useless
• A proposal for evaluating usability testing methods: the practical review system
• Comparative usability evaluation
• Conducting and using usability tests
• Don't test users, test hypotheses
• Eight is not enough
• Experience remote usability testing
• Formal usability reports vs quick findings
• How many users should you test with in usability testing (latest research)
• Observer effects in usability testing
• Quantitative studies: how many users to test
• Recording screen activity during usability testing
• Remote online usability testing: why, how, and when to use it
• Seven common usability testing mistakes
• Six tips to ensure a successful usability test
• Test your designs - on people
• UI guidelines vs usability testing
• Usability testing: myths, misconceptions and misuses
• Beyond the five-user assumption: benefits of increased sample sizes in usability testing (PDF)