Onsite Testing of software is done at various stages of software development. It is most common at the Compliance and Usability Testing phases which are part of User Acceptance Testing. A Subject Matter Expert (SME) or a team of experts test the application to find and remove errors in it.
It is not uncommon to have an SME perform other testing strategies during the software development life-cycle. This can involve the placement of more than one SME depending on the development phase. The errors and problems are recognised during each development process and removed in that particular stage only. This results in a highly competent software that is ready for the final performance test.
Onsite Testing is, due to the placement of the SME in the software development company, more expensive than its economical twin "Remote Application Testing". For companies that put higher emphasis on security, this is an ideal solution. This type of testing is also beneficial for companies that are developing highly customised software where the SME is present to conduct performance testing.