capsys for stdout/stderr in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to capture standard output using capsys in pytest.

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'

Acapture

Breadouterr

Cgetoutput

Dcapture_output

Attempts:

3 left

💡 Hint

Common Mistakes

Using a non-existent method like capture() or getoutput()

Trying to access capsys.out directly without calling a method

The capsys fixture provides the method readouterr() to capture stdout and stderr output.

2fill in blank

medium

Complete the code to capture standard error output using capsys in pytest.

PyTest

def test_error_output(capsys):
    import sys
    print("Error message", file=sys.stderr)
    captured = capsys.[1]()
    assert captured.err == "Error message\n"

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

Areadouterr

Bcapture

Ccapture_err

Dgeterr

Attempts:

3 left

💡 Hint

Common Mistakes

Trying to use a method that only captures stdout

Using a method name that does not exist in capsys

The readouterr() method captures both stdout and stderr; captured.err contains the stderr output.

3fill in blank

hard

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

PyTest

def test_output(capsys):
    print("Test output")
    captured = capsys.[1]()
    assert captured.out == "Test output\n"

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

Agetoutput

Bcapture

Creadouterr

Dcapture_output

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the newline character in the assertion

Using a wrong method to capture output

The captured output includes a newline, so the assertion must match the exact string including '\n'.

4fill in blank

hard

Fill both blanks to capture output and check that stderr is empty.

PyTest

def test_stdout_only(capsys):
    print("Only stdout")
    captured = capsys.[1]()
    assert captured.out == "Only stdout\n"
    assert captured.[2] == ""

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

Areadouterr

Bcapture

Cerr

Dout

Attempts:

3 left

💡 Hint

Common Mistakes

Checking captured.out instead of captured.err for stderr

Using a non-existent method to capture output

Use readouterr() to capture both outputs, then check captured.err for empty stderr.

5fill in blank

hard

Fill all three blanks to capture output, check stdout, and check stderr after printing to both.

PyTest

def test_both_outputs(capsys):
    import sys
    print("Output message")
    print("Error message", file=sys.stderr)
    captured = capsys.[1]()
    assert captured.[2] == "Output message\n"
    assert captured.[3] == "Error message\n"

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

Areadouterr

Bout

Cerr

Dcapture

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing up captured.out and captured.err

Using a wrong method name to capture output

readouterr() captures both outputs; captured.out holds stdout, captured.err holds stderr.