Testing for personality disorders is different from other testing due to the need for information that spans decades. To diagnose a personality disorder, copious records from a variety of sources are needed to show the relatively predictable and enduring traits necessary for such a diagnosis. This is not found only in a careful psychosocial history and the use of testing instruments, but rather the interviewing of multiple individuals in the client’s life, past and present, who can attest to the persistence of the traits under investigation and the impairment they cause.