In Chapter Two, the challenges of test construction were explained, including is

Reliability refers to the consistency of a test over time, from one part of the test to another, and from one scorer to another.
Validity refers to the ability of a test to measure what it is supposed to measure.
One way to demonstrate reliability is to give the same test to a person on two separate occasions or to have the same test scored by two different people.  Projective tests fail both of these measures of reliability.
Scores of projective test are significantly affected by sleepiness, hunger, medication, worry, verbal ability, instructions given, and other factors.  Thus, the scores do not represent personality variables and are not valid.
Many well-known objective tests are both valid and reliable.
Some tests like the MMPI even include special validity scales to determine when someone is lying, defensive, or evasive in answering questions.