Why am I being asked to sit these tests?
Psychometric testing is an equal part of your application, just like your CV, and your interview.
It allows your prospective employer to know more about you, your abilities, and the way you work.
It shows that they would love to get to know you better, and do so in a quick and easy way that respect your time, and the amount of time that you have already put into your application.
The employment relationship is so important, and this shows that your possible new managers want to get to know you that much better.