Dynamic fixture selection in PyTest - Test Execution Trace

Test Overview

This test demonstrates how to select a fixture dynamically in pytest based on a test parameter. It verifies that the correct fixture is used and returns the expected value.

Test Code - pytest

PyTest

import pytest

@pytest.fixture
 def fixture_a():
     return "Data from fixture A"

@pytest.fixture
 def fixture_b():
     return "Data from fixture B"

@pytest.fixture
 def dynamic_fixture(request):
     if request.param == "a":
         return request.getfixturevalue("fixture_a")
     elif request.param == "b":
         return request.getfixturevalue("fixture_b")
     else:
         pytest.skip("Unsupported fixture parameter")

@pytest.mark.parametrize("dynamic_fixture", ["a", "b"], indirect=True)
 def test_dynamic_fixture(dynamic_fixture):
     assert dynamic_fixture in ["Data from fixture A", "Data from fixture B"]

Execution Trace - 9 Steps

Step	Action	System State	Assertion	Result
1	Test starts	pytest test runner initialized	-	PASS
2	pytest collects test_dynamic_fixture with parameter 'a'	Test function ready to run with dynamic_fixture param 'a'	-	PASS
3	pytest calls dynamic_fixture fixture with param 'a'	Inside dynamic_fixture, param is 'a'	-	PASS
4	dynamic_fixture calls fixture_a using getfixturevalue	fixture_a returns 'Data from fixture A'	-	PASS
5	test_dynamic_fixture runs with dynamic_fixture='Data from fixture A'	Test function executing	Assert dynamic_fixture is in ['Data from fixture A', 'Data from fixture B']	PASS
6	pytest collects test_dynamic_fixture with parameter 'b'	Test function ready to run with dynamic_fixture param 'b'	-	PASS
7	pytest calls dynamic_fixture fixture with param 'b'	Inside dynamic_fixture, param is 'b'	-	PASS
8	dynamic_fixture calls fixture_b using getfixturevalue	fixture_b returns 'Data from fixture B'	-	PASS
9	test_dynamic_fixture runs with dynamic_fixture='Data from fixture B'	Test function executing	Assert dynamic_fixture is in ['Data from fixture A', 'Data from fixture B']	PASS

Failure Scenario

Failing Condition: dynamic_fixture receives an unsupported parameter value

Execution Trace Quiz - 3 Questions

What does the dynamic_fixture fixture do when the parameter is 'a'?

A It returns the value from fixture_a

B It returns the value from fixture_b

C It skips the test

D It raises an error

Key Result

Using dynamic fixture selection with request.param and getfixturevalue allows flexible test setups based on parameters, improving test reuse and clarity.