Running tests by marker (-m) in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the pytest marker -m option do?

The -m option in pytest runs only the tests that have a specific marker. It helps to select tests by tags or categories.

beginner

How do you mark a test function with a custom marker in pytest?

Use the @pytest.mark.marker_name decorator above the test function to assign a marker.

beginner

Example: How to run only tests marked as slow using pytest command line?

Run pytest -m slow to execute only tests marked with @pytest.mark.slow.

intermediate

What happens if you run pytest -m 'not slow'?

Pytest runs all tests that do NOT have the slow marker. The not keyword excludes tests with that marker.

intermediate

Why should you register custom markers in pytest.ini?

Registering markers in pytest.ini avoids warnings and documents the purpose of each marker for better test management.

Which pytest command runs only tests marked with fast?

A pytest -k fast

B pytest --fast

C pytest -m fast

D pytest --marker fast

The -m option filters tests by marker name, so pytest -m fast runs tests marked with @pytest.mark.fast.

How do you mark a test as database in pytest?

A @database.mark

B @pytest.database

C @mark.database

D @pytest.mark.database

The correct syntax is @pytest.mark.database to assign the database marker to a test.

What does pytest -m 'slow or network' do?

A Runs tests marked with both slow and network

B Runs tests marked with slow or network

C Runs tests without slow or network markers

D Runs all tests except slow and network

The or operator runs tests that have either slow or network markers.

Why add markers to pytest.ini?

A To avoid warnings and document markers

B To run tests in parallel

C To disable markers

D To speed up test execution

Registering markers in pytest.ini prevents warnings about unknown markers and helps document their use.

What is the result of pytest -m 'not network'?

A Runs tests without the network marker

B Runs only network tests

C Runs all tests

D Runs tests with network and other markers

The not operator excludes tests with the network marker, running only tests without it.

Explain how to use pytest markers to run a specific group of tests.

Think about tagging tests and selecting them by tag.

Describe why and how to register custom markers in pytest configuration.

Consider configuration files and team collaboration.

Practice

1. What does the -m option do when running pytest?

easy

A. Runs only tests with the specified marker

B. Runs tests in a specific directory

C. Runs tests in parallel

D. Generates a test report

Solution

1. Step 1: Understand pytest markers

   Markers are labels you add to tests to group them logically.

2. Step 2: Use -m option

   The -m option runs only tests that have the specified marker label.

3. Final Answer:

   Runs only tests with the specified marker -> Option A

4. Quick Check:

   pytest -m runs tests by marker = A [OK]

Hint: Remember: -m filters tests by marker name [OK]

Common Mistakes:

• Confusing -m with directory or file options
• Thinking -m runs all tests regardless of marker
• Assuming -m runs tests in parallel

2. Which of the following is the correct syntax to run pytest tests marked as slow?

easy

A. pytest --marker slow

B. pytest -m slow

C. pytest -marker slow

D. pytest --m slow

Solution

1. Step 1: Recall pytest command options

   The correct option to select tests by marker is -m, not --marker or others.

2. Step 2: Match syntax to run tests with marker

   The correct command is pytest -m slow to run tests marked as slow.

3. Final Answer:

   pytest -m slow -> Option B

4. Quick Check:

   Use single dash -m for marker filter = D [OK]

Hint: Use single dash -m, not --marker [OK]

Common Mistakes:

• Using --marker instead of -m
• Adding extra dashes like --m
• Confusing option names

3. Given these tests marked as fast and db:

@pytest.mark.fast
def test_a(): pass

@pytest.mark.db
def test_b(): pass

@pytest.mark.fast
def test_c(): pass

What tests run with the command pytest -m "fast and not db"?

medium

A. test_b only

B. No tests run

C. test_a, test_b, and test_c

D. test_a and test_c

Solution

1. Step 1: Understand the marker expression

   The command runs tests marked with fast AND NOT marked with db.

2. Step 2: Check each test's markers

   test_a and test_c have fast only; test_b has db only.

3. Final Answer:

   test_a and test_c -> Option D

4. Quick Check:

   fast and not db = test_a, test_c [OK]

Hint: Use logical operators to combine markers correctly [OK]

Common Mistakes:

• Including tests marked only with db
• Ignoring the 'not' operator
• Assuming all tests run

4. You run pytest -m slow but no tests run, even though some tests have @pytest.mark.slow. What is the most likely cause?

medium

A. Markers are not registered in pytest.ini

B. You used -m instead of --m

C. The tests are skipped by default

D. The test files are missing

Solution

1. Step 1: Check marker registration

   Pytest requires custom markers to be registered in pytest.ini to avoid warnings and ensure correct filtering.

2. Step 2: Understand effect of missing registration

   If markers are not registered, pytest may ignore them or not run tests filtered by them.

3. Final Answer:

   Markers are not registered in pytest.ini -> Option A

4. Quick Check:

   Unregistered markers cause no tests run = C [OK]

Hint: Always register custom markers in pytest.ini [OK]

Common Mistakes:

• Confusing -m and --m options
• Assuming tests are skipped by default
• Not checking test file presence

5. You have tests marked as api, ui, and db. You want to run tests that are either api or ui, but not db. Which command achieves this?

hard

A. pytest -m "api or (ui and not db)"

B. pytest -m "api or ui and not db"

C. pytest -m "(api or ui) and not db"

D. pytest -m "api and ui and not db"

Solution

1. Step 1: Understand operator precedence

   Logical AND has higher precedence than OR, so parentheses are needed to group api or ui together.

2. Step 2: Analyze each option

   pytest -m "(api or ui) and not db" correctly groups (api or ui) and excludes db with and not db.

3. Final Answer:

   pytest -m "(api or ui) and not db" -> Option C

4. Quick Check:

   Use parentheses to group OR conditions = A [OK]

Hint: Use parentheses to group markers with OR before AND [OK]

Common Mistakes:

• Ignoring operator precedence without parentheses
• Using AND instead of OR between api and ui
• Including db tests by mistake