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# -*- coding: utf-8 -*- | |
# To use, at the directory you saved this: | |
# python -m unittest test_stdio | |
import sys | |
import io | |
import unittest | |
def stub_stdin(testcase_inst, inputs): | |
stdin = sys.stdin | |
def cleanup(): | |
sys.stdin = stdin | |
testcase_inst.addCleanup(cleanup) | |
sys.stdin = StringIO(inputs) | |
def stub_stdouts(testcase_inst): | |
stderr = sys.stderr | |
stdout = sys.stdout | |
def cleanup(): | |
sys.stderr = stderr | |
sys.stdout = stdout | |
testcase_inst.addCleanup(cleanup) | |
sys.stderr = StringIO() | |
sys.stdout = StringIO() | |
class StdioTestCase(unittest.TestCase): | |
def test_example(self): | |
stub_stdin(self, '42') | |
stub_stdouts(self) | |
example() | |
self.assertEqual(sys.stdout.getvalue(), '42\n') | |
def helper(self, data, answer, runner): | |
stub_stdin(self, data) | |
stub_stdouts(self) | |
runner() | |
self.assertEqual(sys.stdout.getvalue(), answer) | |
# self.doCleanups() # optional, see comments below | |
def test_various_inputs(self): | |
data_and_answers = [ | |
('hello', 'HELLOhello'), | |
('goodbye', 'GOODBYEgoodbye'), | |
] | |
runScript = upperlower # the function I want to test | |
for data, answer in data_and_answers: | |
self.helper(data, answer, runScript) | |
class StringIO(io.StringIO): | |
""" | |
A "safely" wrapped version | |
""" | |
def __init__(self, value=''): | |
value = value.encode('utf8', 'backslashreplace').decode('utf8') | |
io.StringIO.__init__(self, value) | |
def write(self, msg): | |
io.StringIO.write(self, msg.encode( | |
'utf8', 'backslashreplace').decode('utf8')) | |
def example(): | |
number = raw_input() | |
print number.upper() | |
def upperlower(): | |
raw = raw_input() | |
print (raw.upper() + raw), | |
# Calling doCleanup is optional simply because TestCase will call it by | |
# default. It's there to clean up instantly if it is desired and won't | |
# invoke other cleanup code prematurely. |
@lvreynoso sure, I don't mind, given that this trivial piece of code was originally created to demonstrate to some of my colleagues/friends on how redirection of stdio might be done for testing in Python 2.7, while being compatible with Python 3. However, I honestly don't recommend this solution any more, as the implementation has a tight coupling with the unittest framework (the function argument depends directly on an instance of unittest.TestCase
), and that Python 2 has been fully deprecated.
A better solution going forward would be to implement a context manager that manage the stdio redirection, where an example of how this might be done may be found at issue15805 on the CPython issue tracker. Alternatively, unittest.mock.patch
may be leveraged to achieve what the above example code does, given that the linked documentation provide an example to achieve the redirection of sys.stdout
. If both sys.stdin
and sys.stdout
are needed, the following example shows how it might be done in Python 3:
from io import StringIO
from unittest.mock import patch
with patch('sys.stdin', StringIO('Darcy\n')) as stdin, \
patch('sys.stdout', new_callable=StringIO) as stdout:
name = input('What is your name? ')
print('Hello %s' % name)
assert stdout.getvalue() == 'What is your name? Hello Darcy\n'
assert stdin.read() == '' # all input consumed
Yes, please feel free to use this additional trivial code example should this Python 3.3+ solution is more preferable to your needs.
Thank you so much! I appreciate your thoughtful comments.
You're very welcome! (also apologies for getting your name wrong initially when doing the @ reply)
Hi @metatoaster! Would you be willing to release this code under the MIT license?