Running tests by marker (-m) in PyTest - Test Execution Trace

Test Overview

This test script uses pytest markers to categorize tests. It runs only tests marked with smoke and verifies their output.

Test Code - pytest

PyTest

import pytest

@pytest.mark.smoke
def test_addition():
    assert 1 + 1 == 2

@pytest.mark.regression
def test_subtraction():
    assert 5 - 3 == 2

@pytest.mark.smoke
def test_multiplication():
    assert 2 * 3 == 6

# Command to run: pytest -m smoke

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	Test runner starts pytest with marker filter '-m smoke'	pytest collects tests from the file, filtering only those marked with 'smoke'	—	PASS
2	pytest runs test_addition() marked with 'smoke'	Test environment ready, test_addition executes	assert 1 + 1 == 2	PASS
3	pytest runs test_multiplication() marked with 'smoke'	Test environment ready, test_multiplication executes	assert 2 * 3 == 6	PASS
4	pytest does not collect test_subtraction() because it is marked 'regression', not 'smoke'	test_subtraction is not collected or executed	—	PASS
5	pytest finishes test run and reports results	Only tests with 'smoke' marker ran and passed	2 tests passed, 0 tests skipped	PASS

Failure Scenario

Failing Condition: A test marked with 'smoke' fails its assertion

Execution Trace Quiz - 3 Questions

Which tests are executed when running 'pytest -m smoke'?

A Only tests marked with 'smoke'

B All tests regardless of marker

C Only tests marked with 'regression'

D No tests are executed

Key Result

Using markers with '-m' lets you run specific groups of tests easily, helping focus on important test sets like smoke tests.

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