Let’s first understand what personality is and why it is important for employers in the recruitment process. Personality is the typical way in which a person responds to situations or a person’s preferred way of behaving in particular situations.
Your personality affects your success in the role. For example, if you are comfortable interacting with new people, you are likely to be more successful in sales and business development roles than a person who tends to be relatively reserved and shy. Similarly, if you tend to be methodical, systematic and to pay attention to details, you are likely to be more suitable for engineering roles than a person who is expedient (pays less attention to structure and details).
Personality does not change significantly over time. This is not to say that it never changes, but rather that it is stable enough to be measured in a meaningful way. For employers, it is valuable to know how you are likely to behave over the months and years you will be with their organisation— not just on the day that you are tested.