I am continually amazed at applicants that insist on flying a flight test in absolutely crappy weather. You should always remember there are three outcomes to every FAA evaluation once its started...white slip, pink slip and discontinuance! Remember also that you, as the applicant, are pilot in command and responsible for accepting the weather conditions for the test. You should exercise good judgement here for a happy outcome. Granted, some situations might necessitate accepting an extreme test environment. We had a student from Japan at our school who got down to the absolute last day before getting on the plane to Tokyo. We started this test about a half hour before dusk and completed the "high altitude elements" (steep turns, slow flight, stalls) first so he had some horizon reference. I remember doing the "turns around a point" using the control tower (with permission from the amused controller) and then the navigation element as it got dark. Another test occurred during an east coast blackout. The tower at Ithaca was fuctioning with a handheld radio and the navaids were mostly "Tango Uniform". If the situation is not this desparate though, why go out and fly when the wind is gusting across the runway at 20 knots, or visibility is below 5 miles? You are supposed to demonstrate "good judgement" in a flight test, not superhuman abilities. This is your test, you paid for it. It is the culmination of a lot of work and expense so find a day where you are comfortable and can demonstrate your abilities.
On the other side of the coin, there is a standing (and somewhat true) joke that a pilot examiner will never ever see a crosswind landing demonstrated on a flight test. Crafty applicants may try to pick a day with a favorable wind...or wait for CAVU and no wind. (This happens only twice a year in Upstate New York). Verbally quizzing the correct technique for crosswind landing is certainly not going to reveal an applicant's inflight competence! To ascertain the skill here, you might find yourself diverted to an airport with a crossing runway for a more sure test of your abilities. The answer to all this is to have good technique and a set of personal minimums that are well thought out and realistic. Any competent examiner will be impressed with an applicant that states their personal level of comfort and flies to an acceptable standard within those limits. If the weather deals you an unworkable day...discontinue!