Pytest and tempdir

---

• This is a simple application that reads and writes config files (ini file).
• We can test the parse_file by preparing some input files and check if we get the expected data structure.
• In order to test the save_file we need to be able to save a file somewhere.
• Saving it in the current folder will create garbage files. (and the folder might be read-only in some environments).
• For each test we'll have to come up with a separate filename so they won't collide.
• Using a tmpdir solves this problem.

examples/pytest/mycfg.py

import re

def parse_file(filename):
    data = {}
    with open(filename) as fh:
        for row in fh:
            row = row.rstrip("\n")
            if re.search(r'=', row):
                k, v = re.split(r'\s*=\s*', row)
                data[k] = v
            else:
                pass # error reporting?
    return data

def save_file(filename, data):
    with open(filename, 'w') as fh:
        for k in data:
            fh.write("{}={}\n".format(k, data[k]))

if __name__ == '__main__':
    print(parse_file('a.cfg'))

examples/pytest/a.cfg

name=Foo Bar
email  =   foo@bar.com

examples/pytest/test_mycfg.py

import mycfg
import os

def test_parse():
    data = mycfg.parse_file('a.cfg')
    assert data, {
        'name'  : 'Foo Bar',
        'email' : 'foo@bar.com',
    }

def test_example(tmpdir):
    original = {
        'name'  : 'My Name',
        'email' : 'me@home.com',
        'home'  : '127.0.0.1',
    }
    filename = str(tmpdir.join('abc.cfg'))
    assert not os.path.exists(filename)
    mycfg.save_file(filename, original)
    assert os.path.exists(filename)
    new = mycfg.parse_file(filename)
    assert new == original