capfd for file descriptors in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to capture printed output using capfd fixture.

PyTest

def test_print_output([1]):
    print("Hello, world!")
    out, err = capfd.readouterr()
    assert out == "Hello, world!\n"

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

Acapfd

Btmp_path

Cmonkeypatch

Dcapsys

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'capsys' instead of 'capfd' when file descriptor capture is needed.

Forgetting to include the fixture as a function argument.

The capfd fixture captures output to file descriptors like stdout and stderr.

2fill in blank

medium

Complete the code to capture and check stderr output using capfd.

PyTest

def test_error_output(capfd):
    import sys
    print("Error message", file=[1])
    out, err = capfd.readouterr()
    assert err == "Error message\n"

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

Asys.stdout

Bsys.__stderr__

Csys.stdin

Dsys.stderr

Attempts:

3 left

💡 Hint

Common Mistakes

Printing to sys.stdout instead of sys.stderr.

Confusing sys.stdin with output streams.

To capture error output, print to sys.stderr.

3fill in blank

hard

Fix the error in the code to correctly capture output using capfd.

PyTest

def test_output([1]):
    print("Test")
    out, err = capfd.readouterr()
    assert out == "Test\n"

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

Acapsys

Bcaplog

Ccapfd

Dtmp_path

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'capsys' instead of 'capfd' when file descriptor capture is required.

Not including the fixture argument at all.

The function argument must be capfd to use its readouterr() method.

4fill in blank

hard

Fill both blanks to capture output and check it after printing.

PyTest

def test_multiple_prints([1]):
    print("First line")
    print("Second line")
    out, err = [2].readouterr()
    assert out == "First line\nSecond line\n"

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

Acapfd

Bcapsys

Ccaplog

Dtmp_path

Attempts:

3 left

💡 Hint

Common Mistakes

Mixing different fixtures like capsys and capfd.

Using caplog which is for logging, not output capture.

Both blanks must be capfd to capture and read output correctly.

5fill in blank

hard

Fill all three blanks to capture output, print error, and assert both outputs.

PyTest

def test_output_and_error([1]):
    print("Output line")
    import sys
    print("Error line", file=sys.stderr)
    out, err = [2].readouterr()
    assert out == "Output line\n"
    assert err == [3]

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

Acapfd

Bcapsys

C"Error line\n"

D"Output line\n"

Attempts:

3 left

💡 Hint

Common Mistakes

Using capsys instead of capfd when file descriptor capture is needed.

Forgetting the newline character in the error string assertion.

The fixture capfd captures both stdout and stderr. The error output string must match exactly.