Brent has discussed formal and informal assessments. Informal assessments are probably okay, as long as you don’t ask the “forbidden” questions that would trigger discrimination concerns. I want to dwell a bit more on the formal assessments, and how they might cause concern from a legal standpoint.
Vocational or personality testing doesn’t usually raise an issue. In many ways, those tests are designed to a person useful information about themselves, and give the employer helpful information about the person. For instance, my five strengths on the Strength Finder are Achiever, Strategic, Learner, Connectedness, and either Input or Relator, which probably tells you a lot about why I started a law firm.
The more ominous tests are the diagnostic ones that might identify illnesses and disabilities. These tests can trigger concerns under the Americans with Disabilities Act (ADA) or the Genetic Information Nondiscrimination Act (GINA)—or similar laws in other countries. Brent and I have a whole series of posts discussing GINA, but you should not collect information that involves GINA.
To avoid concerns about ADA discrimination, you want to do your candidate testing after you have made a “job offer.” This is not always the sequence that missions use. Sometimes, missions will segregate the test results until a decision is made, but this still goes against EEOC guidance. https://www.eeoc.gov/policy/docs/medfin5.pdf
Employers can use medical testing (of which psychological testing is a subset), but it has to be used consistently for all candidates, and must be for a job-related reason. For instance, if a particular field placement requires a certain level of physical and psychological health, the job description should be clear on what is needed, and why. There may be fields of service where certain types of physical or mental illnesses cannot be adequately supported, for instance.
All this must be very carefully defined and described, or you may be guilty of discrimination. Your religious hiring criteria (and your ministerial exception) should also be in place. You can set certain limitations on whom you send to the field, and you may be legally responsible if you knowingly send someone fragile and there is a disaster. What you can’t legally do is use your testing to weed out anyone with physical or mental disabilities.
This leads naturally into topics of accommodation and interactive discussions about disability.
Disclaimer: not official legal or psychological advice or opinion