In buying a software testing service, the first factor to look out for is the experience of the Agency. Unlike other disciplines, the more one practices bug detection, the more exposure the individual becomes exposed to unconventional errors. software could behave erratically; totally deviant from the intended purpose. An engineer with years of work is able to appreciate such fats easily.
Documentation is another criteria to pay attention to. At the close of the test, the quality assurance agency should deliver a Report that specifies the error. Information about the location of the error, the trigger, the severity and the resultant consequences must al be detailed out for stakeholders.