Frank Szmulowicz, Ph. D. Jun 19, 2014:

A fair test is a test that is conducted with a controlled environment. It means that the conditions in each test are identical except for the one variable that is being tested. The conditions are fair.
http://www.ask.com/question/what-is-the-definition-of-a-fair...

Frank Szmulowicz, Ph. D. Jun 17, 2014:

A fair test, besides being fair, denotes a particular way of conducting an experiment, etc. The question is whether there is a one-to-one technical correspondence between a fair test and test rzetelny. If not, perhaps a short descriptive definition is in order.

Elzbieta Reiner Jun 16, 2014:

Ja bym przetłumaczyła "w teście rzetelnym, uczeń dostrzega,...". Zostawiłabym "enquiry", bo wychodzi mi masło maślane.