The only check rides I've done in darkness has been the Instrument ride. It's pretty effective at seeing how an applicant will do on instruments without actually being in the clouds.
One issue that comes up is remembering to turn on the approach and runway lights. It may not be an issue if you're flying at a towered airport but at the non towered, the lights are up to you. I usually pop the lights up with 7 clicks at Glideslope intercept or FAF inbound. I'll make a position report first just to make sure I don't tick off another pilot in the pattern.
If you get down to the DA or MAP and you don't see the lit runway, go-around. There are several accidents where pilots have attempted to land on an unlit runway only to miss the runway entirely or hit something. Not good.
Probably one of the tougher check rides out there from both the applicants side and the DPE's. Where do I see problems on the initial CFI? Its with the known required material. For example: Area of Operation (AOO) II "Technical Subject Areas"; Task M "Logbook Entries and Certificate Endorsements". For a well prepared applicant this topic will take 10 minutes but I've seen applicants struggle on the subject for 45 minutes. I will usually tie that Task with AOO III "Preflight Preparation"; Task A "Certificates and Documents" which covers the requirements for each pilot certificate, medical and logbook entries. Makes sense right? What are the regulatory and endorsements requirements for a pilot taking a private pilot checkride.?
I like to test the basics. If an applicant cant teach basic flying material, how can they teach the complex? For example, I'll ask the applicant to demonstrate how to use a Take off Distance or Cruise chart. Almost all Charts require the pilot to determine Pressure Altitude. Do you know how to calculate pressure altitude? I know of a few pilots that can't. How does this look on a CFI check ride?
The instructing requirements for the oral is that the applicant is clear, concise and technically accurate.
The flight part of the Initial CFI ride is usually where most applicants shine, however, when an applicant blows it, they blow it big time. I've seen CFI applicants lose 400 feet in steep turns, Stall at the top of a Chandell and enter an incipient spin from a power off stall. Not Cool. Remember the tolerances for the CFI ride are that the applicant must fly to commercial pilot standards while teaching.
Recommending Instructors, How do you know your applicant is ready for the Initial CFI check ride? It's simple. You give the student a subject and they can explain it correctly in simple terms with minimum use of notes and no help from you. If the applicant give an unclear answer, challenge them with a question. If the applicant knows the material they'll be able to answer the question easily. If they can't, you've discovered a weak area that a DPE will take advantage of on the checkride.