The past life test works on the assumption that human behaviour at a subconscious level is affected by past lives. Thereby, working backwards and asking questions related to your current behaviour, the past life test tries to determine who you might have been in your previous incarnation. Past life tests are considered pseudoscience as there is no evidence regarding the existence of past lives
Almost all past life tests ask multiple questions ranging from your love for animals to your ideal occupation, to countries you would like to visit, to your sartorial preferences to figure out who you once were. These tests depend on you answering the questions asked in an honest and transparent manner to come up with results with any degree of accuracy.
Certain religions like Hinduism and Buddhism talk about reincarnation or rebirth of the eternal soul called the jiva. After a person's death, the jiva leaves his material body and enters a higher realm. Based on the actions in his prior life, the soul or jiva either breaks free from the cycle or birth-death-rebirth or descends again into the world taking a life form. Since the soul is continuous and unchanged from prior birth, the answers to past life tests help determine what earthly form the soul had inhabited in a past life.