Built-in markers (skip, skipif, xfail) in PyTest

Introduction

Sometimes tests should not run or are expected to fail. Built-in markers help control this easily.

Skip a test that needs a feature not yet implemented.

Skip a test only on certain operating systems or Python versions.

Mark a test as expected to fail because of a known bug.

Temporarily skip tests that depend on external services that are down.

Avoid running slow tests during quick checks by skipping them.

Syntax

PyTest

import pytest

@pytest.mark.skip(reason="reason text")
def test_example():
    assert True

@pytest.mark.skipif(condition, reason="reason text")
def test_conditional():
    assert True

@pytest.mark.xfail(condition=None, reason="reason text", strict=False)
def test_expected_fail():
    assert False

skip always skips the test with a reason.

skipif skips the test only if the condition is True.

xfail marks a test as expected to fail; it won't fail the test suite if it does.

Examples

This test will always be skipped with the reason 'Not ready yet'.

PyTest

import pytest

@pytest.mark.skip(reason="Not ready yet")
def test_skip():
    assert 1 == 1

This test runs only if the platform is not Windows.

PyTest

import sys
import pytest

@pytest.mark.skipif(sys.platform == "win32", reason="Does not run on Windows")
def test_skipif():
    assert True

This test is expected to fail because of a known bug.

PyTest

import pytest

@pytest.mark.xfail(reason="Bug #123")
def test_xfail():
    assert False

This test is expected to fail, but if it passes, pytest will mark it as an error because strict=True.

PyTest

import pytest

@pytest.mark.xfail(strict=True, reason="Fix soon")
def test_xfail_strict():
    assert True

Sample Program

This script shows all three markers:

• test_always_skip is always skipped.
• test_skipif_version runs only if Python version is 3.8 or higher.
• test_expected_failure is expected to fail and won't break the test suite.
• test_xfail_strict is expected to fail but passes, so pytest will report an error because of strict=True.

PyTest

import sys
import pytest

@pytest.mark.skip(reason="Skipping this test always")
def test_always_skip():
    assert False

@pytest.mark.skipif(sys.version_info < (3, 8), reason="Needs Python 3.8+")
def test_skipif_version():
    assert True

@pytest.mark.xfail(reason="Known bug in feature")
def test_expected_failure():
    assert False

@pytest.mark.xfail(strict=True, reason="Should fix soon")
def test_xfail_strict():
    assert True

Important Notes

Always provide a clear reason to explain why a test is skipped or expected to fail.

Use skipif for conditions like OS, Python version, or missing dependencies.

With xfail(strict=True), a passing test will cause pytest to fail, helping track bug fixes.

Summary

Built-in markers help control test execution flow simply.

skip always skips, skipif skips conditionally, xfail marks expected failures.

Use them to manage tests during development and known issues.

Practice

1. What does the @pytest.mark.skip marker do in a test?

easy

A. It retries the test multiple times before failing.

B. It runs the test only if a condition is true.

C. It marks the test as expected to fail but still runs it.

D. It always skips the test, so it does not run.

Solution

1. Step 1: Understand the purpose of @pytest.mark.skip

   This marker tells pytest to skip the test unconditionally, so the test is not executed at all.

2. Step 2: Compare with other markers

   skipif skips conditionally, and xfail marks expected failures but runs the test. So only skip always skips.

3. Final Answer:

   It always skips the test, so it does not run. -> Option D

4. Quick Check:

   @pytest.mark.skip always skips = D [OK]

Hint: Skip always means test won't run at all [OK]

Common Mistakes:

• Confusing skip with skipif (conditional skip)
• Thinking xfail skips the test
• Assuming skip reruns the test

2. Which of the following is the correct syntax to skip a test only if Python version is less than 3.8?

easy

A. @pytest.mark.skipif(sys.version_info < (3, 8)\ndef test_func(): pass

B. @pytest.mark.skipif(sys.version_info < (3, 8), reason='Python < 3.8')\ndef test_func(): pass

C. @pytest.mark.skipif(sys.version_info < 3.8)\ndef test_func(): pass

D. @pytest.mark.skipif(sys.version_info < '3.8')\ndef test_func(): pass

Solution

1. Step 1: Check correct version tuple comparison syntax

   Python version info is a tuple like (3, 7, 5). So comparisons must use tuples, e.g., (3, 8).

2. Step 2: Verify correct use of skipif with reason

   @pytest.mark.skipif(sys.version_info < (3, 8), reason='Python < 3.8')\ndef test_func(): pass uses tuple comparison and includes a reason string, which is best practice for clarity.

3. Final Answer:

   @pytest.mark.skipif(sys.version_info < (3, 8), reason='Python < 3.8')\ndef test_func(): pass -> Option B

4. Quick Check:

   Use tuple and reason in skipif = C [OK]

Hint: Use tuple for version and add reason in skipif [OK]

Common Mistakes:

• Using float instead of tuple for version
• Omitting reason argument
• Comparing version to string

3. What will be the test result when running this code?

import pytest

@pytest.mark.xfail
def test_example():
    assert 1 == 2

medium

A. Test is marked as expected failure but does not fail the suite.

B. Test fails and is reported as failed.

C. Test passes because xfail ignores failures.

D. Test is skipped and not run.

Solution

1. Step 1: Understand @pytest.mark.xfail behavior

   This marker means the test is expected to fail. If it fails, pytest reports it as an expected failure, not a hard failure.

2. Step 2: Analyze the assertion

   The assertion 1 == 2 is false, so the test fails. Because of xfail, this failure is expected and reported accordingly.

3. Final Answer:

   Test is marked as expected failure but does not fail the suite. -> Option A

4. Quick Check:

   xfail means expected failure = A [OK]

Hint: xfail means failure is expected, not a hard fail [OK]

Common Mistakes:

• Thinking xfail skips the test
• Assuming test passes despite assertion
• Confusing xfail with skipif

4. Identify the error in this pytest code snippet:

import pytest

@pytest.mark.skipif(sys.platform == 'win32')
def test_func():
    assert True

medium

A. Missing import of sys module causes NameError.

B. skipif should be skip to always skip the test.

C. The condition syntax is incorrect; should use double equals.

D. The test function must return a value.

Solution

1. Step 1: Check imports used in condition

   The condition uses sys.platform, but sys is not imported, causing a NameError at runtime.

2. Step 2: Verify other parts

   The condition syntax is correct with ==, skipif is valid, and test functions do not need to return values.

3. Final Answer:

   Missing import of sys module causes NameError. -> Option A

4. Quick Check:

   Missing import sys = A [OK]

Hint: Always import modules used in skipif conditions [OK]

Common Mistakes:

• Forgetting to import sys
• Confusing skipif with skip
• Expecting test functions to return values

5. You want to mark a test that should be skipped on Windows and expected to fail on Python versions below 3.7. Which is the correct way to combine skipif and xfail markers?

hard

A. @pytest.mark.xfail(sys.version_info < (3,7, reason='Expected fail on old Python')\[e-mail](sys.platform == 'win32', reason='Skip on Windows')\ndef test_func(): pass

B. @pytest.mark.skipif(sys.platform == 'win32' and sys.version_info < (3,7))\ndef test_func(): pass

C. @pytest.mark.skipif(sys.platform == 'win32', reason='Skip on Windows')\[e-mail](sys.version_info < (3,7), reason='Expected fail on old Python')\ndef test_func(): pass

D. @pytest.mark.skipif(sys.platform == 'win32')\[e-mail](sys.version_info < (3,7))\ndef test_func(): pass

Solution

1. Step 1: Understand marker order and logic

   Tests should be skipped on Windows unconditionally, so skipif for Windows must be applied first.

2. Step 2: Apply xfail conditionally for Python versions below 3.7

   The xfail marker is applied second to mark expected failures on old Python versions.

3. Step 3: Verify option correctness

   @pytest.mark.skipif(sys.platform == 'win32', reason='Skip on Windows')\[e-mail](sys.version_info < (3,7), reason='Expected fail on old Python')\ndef test_func(): pass applies skipif first, then xfail, both with reasons. This is the correct and clear approach.

4. Final Answer:

   Use skipif for Windows, then xfail for Python version condition with reasons. -> Option C

5. Quick Check:

   Skip first, then xfail with reasons = B [OK]

Hint: Apply skipif first, then xfail with clear reasons [OK]

Common Mistakes:

• Reversing marker order causing unexpected runs
• Combining conditions incorrectly in one skipif
• Omitting reason strings for markers