Python 单元测试模块而不是 function

Question

I'm trying to write a test.py file to test a module I wrote. The specifications of the program are that I take serial user input and then print, not return a single answer. The first line of user input indicates how many inputs will follow. With an example program, "4\n1\n2\n3\n4\n" would mean there are 4 inputs and the inputs are [1,2,3,4]. Here is an example of the program that would take the input (sumEx.py):

import sys
def sum():

    n = int(sys.stdin.readline().strip())
    nums = []
    for _ in range(n):
        nums.append(int(sys.stdin.readline().strip()))

    result = 0
    for num in nums:
        result += num
    
    print(result)

if __name__ == "__main__":
    sum()

I realize that in this example the for loop is redundant, but this is just an example for the actual program I am working on to abstract the problem. Currently, this is the test file I have:

from io import StringIO
import sys
from _pytest.monkeypatch import MonkeyPatch
import unittest
from sumEx import sum as program

class Testing(unittest.TestCase):
    def test_string(self):
        monkeypatch = MonkeyPatch()
        monkeypatch.setattr('sys.stdin', StringIO("8\n1\n2\n3\n4\n5\n6\n7\n8\n"))
        self.assertEqual(program(), 36)

    def test_boolean(self):
        monkeypatch = MonkeyPatch()
        monkeypatch.setattr('sys.stdin', StringIO("4\0\n1\n2\n3\n"))
        self.assertEqual(program(), 6)

if __name__ == '__main__':
    unittest.main()

The problem is that my tests will only work if I returned them instead of printing them. Ideally, my test file would call the file sumEx.py and then

if __name__ == "__main__":
    sum()

would call the sum function, the test would supply the input (like an actual person typing each line), and then whatever sum prints would be considered the output for the test. Any help is greatly appreciated. Please ask any questions if something is too vague. Thank you!

Answer 1

If anyone is curious, this is what I'm gonna go with for now. This takes input from a file and mimics user input through sys.stdin. It then reads the correct output from a file and compares it to the output of the program. It also runs the same test case with different inputs with the help of parameterization. Thank you @MrBeanBremen for the suggestion!

class Testing(unittest.TestCase):

    def load_file(self, fileName, inOut):
        try:
            inputFile = open(fileName, 'r')
            fileInput = r'{}'.format(inputFile.readline())
            for line in inputFile.readlines():
                fileInput = r'{}'.format(fileInput + line)
            if inOut == 'in':
                fileInput = r'{}'.format(fileInput+'\n')
            inputFile.close()
            return fileInput
        except:
            print("ERROR LOADING FILE")
        
    @parameterized.expand([
        ["./tests/test0in.txt", "./tests/test0out.txt"],
        ["./tests/test1in.txt", "./tests/test1out.txt"],
        ["./tests/test2in.txt", "./tests/test2out.txt"]])
    @patch('sys.stdout', new_callable=StringIO)
    def test(self, inputFile, outputFile, mock_stdout):
        monkeypatch = MonkeyPatch()

        monkeypatch.setattr('sys.stdin', StringIO(self.load_file(inputFile, "in")))
        program.main()
        self.assertEqual(mock_stdout.getvalue(), self.load_file(outputFile, "out"))
    
if __name__ == '__main__':
    unittest.main(verbosity=2)