Python单元测试：为模拟输入设计目录结构吗？

Question

I am writing production code that parses a large file, which itself contains many different cases. To unittest the production code, I want to write a test case for each case. My question case is what a good way is to set up the testing directory and the testing code.

The current directory structure is:

root/
    src/
        parser.py
    test/
        test_parser.py
        raw/
            case_1.csv
            case_2.csv
            ...

The testing code looks like this:

from parser import parse
import unittest import TestCase


class Test_Parser(TestCase):

   def setUp(self):
       raw_dir = 'raw'

   def test_case_1(self):
       filename = self.raw_dir + '/case_1.csv'
       actual = parse(filename)
       # assert actual == expected

   def test_case_2(self):
       filename = self.raw_dir + '/case_2.csv'
       actual = parser(filename)
       # assert actual == expected

   ...

Is there a more Pythonic way to factor the directory self.raw_dir out, so that the test case is cleaner and one only has to write filename = 'case_1.csv' ?

Answer 1

If you want to avoid writing the whole path in your test methods, which is understandable, you could isolate this in a separate method which doesn't begin with _test and therefore won't be called when executing the tests:

import os
import parser
import unittest

class TestParser(unittest.TestCase):

    def setUp(self):
        self.raw_dir = "raw"

    def get_path(self, filename):
        path = os.path.join(self.raw_dir, filename)
        return path

    def file_parse(self, filename):
        # every method of this class being supposed to call
        # the parser, it makes sense to isolate these calls
        # into a specific method to avoid repetition
        # - won't be the same is the class is more general-purpose
        path = self.get_path(filename)
        actual = parser.parse(path)
        return actual

    def test_case_1(self):
        actual = self.file_parse(filename='case_1.csv')
        # assert actual == expected

    def test_case_2(self):
        actual = self.file_parse(filename='case_2.csv')
        # assert actual == expected

The main idea here is separation of concerns . One specific method to take care of the "putting dirs and filenames into a correct path" labour, another one to do the parsing and the test methods to do the actual tests (and only that).

Note that as suggested, you should use os.path.join ( documentation ) instead of hardcoding the slashes / .

Also, according to PEP8 , class names should be CamelCase , not under_score or A_Mix_Of_Both .