You need a third table to sit between People and Tests to bridge the gap in order for this to work:
People::kp_person_id = People_Test::kf_Person_id
Test::kp_TestID = People_Test::kf_Test_id
You can then place a portal to People_Test on a People layout, and add fields from Tests to list the tests this person has taken. (You can put fields in People_Test to document details--such as a test score that are specific to that particular time that they took the test.)
Similarly, a portal to People_Test placed on a Tests layout can include fields from People to list the people who have taken that particular test.
Here's a demo file, it matches contracts to companies, but if you were to rename those tables, People and Tests, it'd match what I'm describing here: http://www.4shared.com/file/PLhjErzu/Contracts_to_Companies.html
Great thank you. Most of my database is set up this way. I thought that I could do a one-to-many relationship because there is only one possible test they could ever take (the certification).
Thanks for your help!
I mis-read your original post.
If you are only recording test results, then
People::kp_person_id = Tests::kf_Person_id
Peopleshould work for you.