Testing During Development(valid,valid extreme,invalid,invalid extreme,erroneous

Hiya writing a program and am supposed to do 3-5 during development tests whilst executing (F5) but i don't use an input from the user at all how can i use the 5 following tests: Erroneous,Invalid,Invalid Extreme, Valid Extreme, Valid so far whilst running ive come up with the following error:

Traceback (most recent call last):
File "C:\Users/program.py", line 24, in <module>
print(read_file())
 File "C:\Users\\program.py", line 21, in read_file
 sorted_list.append(haggis_population)
  NameError: global name 'sorted_list' is not defined

what type of test is this? and is this a valid possible test?