Built-in markers (skip, skipif, xfail) in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the pytest marker @pytest.mark.skip do?

It tells pytest to skip the test unconditionally, so the test will not run at all.

beginner

How does @pytest.mark.skipif(condition) work?

It skips the test only if the given condition is true. If false, the test runs normally.

beginner

What is the purpose of @pytest.mark.xfail?

It marks a test as expected to fail. If the test fails, pytest reports it as an expected failure, not a test failure.

intermediate

When would you use skipif instead of skip?

Use skipif when you want to skip a test only under certain conditions, like missing dependencies or specific OS.

intermediate

What happens if a test marked with xfail passes?

Pytest reports it as an unexpected pass, which means the test was expected to fail but did not.

What does @pytest.mark.skip do?

A Runs the test only if a condition is true

B Marks the test as expected to fail

C Skips the test unconditionally

D Runs the test twice

skip skips the test no matter what.

When does @pytest.mark.skipif(condition) skip a test?

A Only if the condition is true

B Never

C Only if the condition is false

D Always

skipif skips only when the condition is true.

What does @pytest.mark.xfail indicate?

A Test should be skipped

B Test is expected to fail

C Test must pass twice

D Test is flaky

xfail marks tests expected to fail.

If a test marked with xfail passes, pytest reports it as:

A Skipped

B Fail

C Pass

D Unexpected pass

Passing an xfail test is an unexpected pass.

Which marker would you use to skip a test only on Windows OS?

A @pytest.mark.skipif(sys.platform == 'win32')

B @pytest.mark.xfail

C @pytest.mark.skip

D @pytest.mark.run

skipif with a condition checks the OS and skips accordingly.

Explain the differences between skip, skipif, and xfail markers in pytest.

Think about when and why you would skip or expect failure.

Describe a real-life scenario where you would use @pytest.mark.skipif.

Consider tests that depend on external conditions.

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