Making pytest wait for user input

Question

I am writing some tests that rely on user input to decide whether they have passed.

I have this function:

def viewable(actual_proj):
    print("\nCan you see %s projects named:\n"%len(actual_proj))
    for i in actual_proj:
        print (i+"\n")
    return input("(y/n)? : ")

Within :

def is_present(pytestconfig, project_not_present = 0):

    actual_projects = all_projects.copy()
    if (project_not_present!=0):
        del_file = all_ini_files[project_not_present-1]
        os.rename(del_file, del_file +'_tst')
        del actual_projects[project_not_present-1]
    capmanager = pytestconfig.pluginmanager.getplugin('capturemanager')

    subprocess.Popen('./MultiPRM.exe')
    capmanager.suspendcapture(in_=True)

    decision = viewable(actual_projects)
    capmanager.resumecapture()
    if (project_not_present!=0):
        os.rename(del_file+'_tst', del_file)
    if (decision =='y'):
        return True
    else:
        return False

When i run the command pytest name_of_test_file.py it runs fine, and stops after each test to get user input. However, i want to use a file which sets up various variables and headers for a log file (called run_tests.py)

# start the report
print("Creating test report: " + os.path.abspath(report_filepath))
rep = open(report_filepath, "w")
rep.write(report_header)
rep.write("Test environment: \n");
rep.write("  Username: " + os.environ['USERNAME'] + "\n")
rep.write("Testing started at: " + get_time() + "\n\n")
rep.close()

# get application version
cmd = exe_under_test + " --help >> " + report_filepath
os.system(cmd)

# start the tests
cmd = "pytest >> " + report_filepath 
os.system(cmd)

# finalise the report
rep = open(report_filepath, "a+")
rep.write("\nTesting completed at: " + get_time() + "\n\n")
rep.close()

When i run it this way, it does not stop or run any of the tests.

If i could write to a log file while also writing the same thing to the terminal(including user input) that would be great. Otherwise, a way of calling this function correctly would work too.

The whole point of unittests is that they don't require user interaction... — Nils Werner, Sep 04 '17 at 11:18
The only way this function can be tested is this way, as incorrect as it may be — Peter Kentish, Sep 04 '17 at 11:40
You really need to find a way to simulate user input for the purposes of the test. If you're relying on user input during the test, then someone else running your test may not be testing the same thing as you. Tests are supposed to be deterministic. — larsks, Sep 04 '17 at 12:11
@PeterKentish write your own implemention of `input()` that returns deterministic results. — Nils Werner, Sep 04 '17 at 12:31
@NilsWerner what do you mean? It is testing something in a GUI, and I have no GUI testing software. — Peter Kentish, Sep 04 '17 at 12:41
I also disagree with never allowing input. For example, in physical product manufacturing, if you need to test a physical click wheel's interaction with your software, you could either connect a DC stepper motor to the click wheel and control it in the test function and verify response (hard and expensive in hardware production environments) or prompt the tester to turn the click wheel and verify response (easy and cheap in hardware production environments). The former is "more proper", but budgets, time, and complexity constraints are real, so... — jacob, May 26 '23 at 22:42

score 3 · Accepted Answer · answered Sep 07 '17 at 06:51

Your tests should be as easy to run as possible to make it hassle free to execute them. If they will be dependent on external (e.g. user's) input and some other tricks to properly run, then nobody is going to execute them in the long run.

If you are the sole developer in the project you can probably live with it, but I would say that this approach is incorrect and not considered to be the best-practices.

First of all if you are just waiting for user's input in the console (which seems like from your code snippets), then just mock the input built-in and set it return value, e.g.:

app.py

def my_input(prompt=''):
    try:
        return raw_input(prompt)
    except NameError:
        return input(prompt)


def my_great_func():
    choice = my_input('y/n?: ')
    return choice

test.py

import unittest.mock as mock    
import pytest

from app import my_great_func

@pytest.yield_fixture
def fake_input():
    with mock.patch('app.my_input') as m:
        yield m


def test_my_great_func(fake_input):
    fake_input.return_value = 'y'
    assert my_great_func() == 'y'

Test execution:

$ pytest test.py -v
============================= test session starts ==============================
platform linux -- Python 3.5.2, pytest-3.2.1
cachedir: .cache
rootdir: /home/kris/projects/tmp, inifile:
collected 1 item                                                                

test.py::test_my_great_func PASSED

=========================== 1 passed in 0.01 seconds ===========================

And secondly strive to write code where your application logic and GUI are loosely coupled - this way you can test your logic regardless of the GUI (be it web, desktop or mobile app).

score 1 · Answer 2 · answered Nov 08 '21 at 04:39

Unit test shouldn't require inputs but if you need it temporarily this is a way. If you use the flag -s it will output as it goes rather than capturing and only displaying on failures. So if you use pytest -s you can call input() and it will pause and wait for input before proceding.

Making pytest wait for user input

2 Answers2