CODEWITHSUNDEEP
pythonunit-testingassertions
salce
salce

Reputation: 407

Checking if correct value is outputed Python unit test

I tried to word the title as clearly as possible. I'm new to unit testing, and I have a handle on some of the more basic types of assertions, but there is one test I haven't figured out. So I have user enter some type of input and I print the output by calling the variable preceding some type of message. Here is the py file the testsuite is testing

def get_input()
    pirateInput = input("What be ye name?! ")
    print("Ahoy Captain ", pirateInput)

The user enters a name and I just print it out. So the expected output should be "Ahoy Captain [user input]"

Here is my test suite

import unittest
from unittest.mock import patch

from get_input import *

class GetInputTest(unittest.TestCase):

    def test_ValuePrints(self):
      #patch input as 'Hook'
      @patch('builtins.input', return_value='Hook'

          saved_stdout = sys.stdout
      try:
          out = io.StringIO()
          sys.stdout = out
          get_input()
          output = out.getvalue().strip()
          assert output == 'Ahoy Captain Hook'
      finally:
          sys.stdout = saved_stdout

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

So I check for the output I'm expecting, but the test does patch the input as expected. I don't know if I'm clear but hopefully someone can help. If you need more detail please let me know.

Thanks

Upvotes: 1

Views: 1990

Answers (1)

José Tomás Tocino
José Tomás Tocino

Reputation: 10069

The problem is pretty simple. The print function already adds a space between each pair of arguments, so if you do

print("Ahoy Captain ", pirateInput)

It will print: Ahoy Captain Hook. Notice the two spaces, the one you add at the end of the first string and the one added by print. Just remove the one in your string and it will work.

Here's a full working example:

import unittest
import sys
import io
import logging

from unittest.mock import patch

def get_input():
    pirateInput = input("What be ye name?! ")
    print("Ahoy Captain", pirateInput)

class GetInputTest(unittest.TestCase):

    @patch('builtins.input', return_value='Hook')
    def test_ValuePrints(self, sth):
      log = logging.getLogger( "SomeTest.testSomething" )
      saved_stdout = sys.stdout
      try:
          out = io.StringIO()
          sys.stdout = out
          get_input()
          output = out.getvalue().strip()
          log.debug(output)
          assert output == 'Ahoy Captain Hook'
      finally:
          sys.stdout = saved_stdout

if __name__ == "__main__":
    logging.basicConfig( stream=sys.stderr )
    logging.getLogger( "SomeTest.testSomething" ).setLevel( logging.DEBUG )
    unittest.main()

Test run:

$ python3 main.py 
DEBUG:SomeTest.testSomething:Ahoy Captain Hook
.
----------------------------------------------------------------------
Ran 1 test in 0.000s

OK

Upvotes: 1

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