Since my daughter has completed TT Algebra 1 and 2, I will tell you what we did.
When my daughter struggled on a test, I would review all of the problems in the chapter looking for a trend. If I could tell that she was missing a concept or struggled in one area or completely lost, I would have her start the entire chapter over.
It was never pretty, but since everything builds, missing a foundational point became so critical, my daughter would agree to start over. My daughter successfully passed both TT 1 and 2, so it worked for us.