Why capturing output validates behavior in PyTest - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to capture printed output in a pytest test function.

PyTest

def test_print_output(capsys):
    print('Hello, world!')
    captured = capsys.[1]()
    assert captured.out == 'Hello, world!\n'

Drag options to blanks, or click blank then click option'

Areadouterr

Bcapture

Cgetoutput

Dread

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent method like capsys.capture()

Trying to read output without calling a method

The capsys.readouterr() method captures the output printed to stdout and stderr during the test.

2fill in blank

medium

Complete the assertion to check that the captured output contains the expected substring.

PyTest

def test_partial_output(capsys):
    print('Test output for pytest')
    captured = capsys.readouterr()
    assert [1] in captured.out

Drag options to blanks, or click blank then click option'

A'pytest'

Bcaptured.out

C'output'

D'fail'

Attempts:

3 left

💡 Hint

Common Mistakes

Checking for a string not present in the output

Using the whole output instead of a substring

We check that the string 'pytest' is part of the captured output.

3fill in blank

hard

Fix the error in the test code to correctly capture and assert printed output.

PyTest

def test_error_output(capsys):
    print('Error occurred')
    captured = capsys.[1]()
    assert captured.err == ''

Drag options to blanks, or click blank then click option'

Areadouterror

Breadouterr

Creadoutput

Dcapture

Attempts:

3 left

💡 Hint

Common Mistakes

Misspelling the method name

Using a method that does not exist

The correct method to capture output is readouterr(). It returns both stdout and stderr.

4fill in blank

hard

Fill both blanks to capture output and assert it matches the expected string.

PyTest

def test_output_match(capsys):
    print('Success!')
    captured = capsys.[1]()
    assert captured.[2] == 'Success!\n'

Drag options to blanks, or click blank then click option'

Areadouterr

Bout

Cerr

Dcapture

Attempts:

3 left

💡 Hint

Common Mistakes

Checking captured.err instead of captured.out

Using a wrong method name for capturing

Use readouterr() to capture output and check captured.out for stdout content.

5fill in blank

hard

Fill all three blanks to capture output, strip whitespace, and assert the exact message.

PyTest

def test_strip_output(capsys):
    print('  Trim me  ')
    captured = capsys.[1]()
    output = captured.[2].[3]()
    assert output == 'Trim me'

Drag options to blanks, or click blank then click option'

Areadouterr

Bout

Cstrip

Drstrip

Attempts:

3 left

💡 Hint

Common Mistakes

Using rstrip() which only removes trailing spaces

Forgetting to call the method with parentheses

We capture output with readouterr(), access out, then use strip() to remove spaces.