Oh, interesting one.
I would say "the passing", as a native speaker, but not sure if that is correct. Hopefully someone else can shed light on this gramatically?
According to the dictionary, passage is the act of passing, which would mean that after you had finished passing something, you would use passage.
i.e. "They passed the test. After the passage of the test, they continued with their studies at University."
Student or Learner