Code coverage for mutable variables

mutable_variables.py

# I've developed an unreasonable preference for helper functions over mutable
# variables. It turns out that there's one good reason why. This version of the
# code shows full code coverage.
topics = []
if part_of_a_group:
   topics = collected_works()
    
publish(topics)

# In this version of the code, the coverage tool shows that the "false" branch
# of the if statement is never taken.

def topics(part_of_a_group):
  if part_of_a_group:
    return collected_works()
  return []

publish(topics(part_of_a_group))