Dynamic fixture selection in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to define a pytest fixture named 'data' that returns a list.

PyTest

import pytest

@pytest.fixture
def data():
    return [1]

Drag options to blanks, or click blank then click option'

A[1, 2, 3]

B(1, 2, 3)

C{1, 2, 3}

D'123'

Attempts:

3 left

💡 Hint

Common Mistakes

Using a tuple or set instead of a list.

Returning a string instead of a list.

The fixture should return a list, so the correct answer is a list literal [1, 2, 3].

2fill in blank

medium

Complete the code to select a fixture dynamically based on the 'request' parameter.

PyTest

import pytest

@pytest.fixture
def dynamic_data(request):
    fixture_name = 'data_' + request.param
    return request.getfixturevalue([1])

Drag options to blanks, or click blank then click option'

A'fixture_name'

Bfixture_name

Crequest.param

D'data_'

Attempts:

3 left

💡 Hint

Common Mistakes

Passing the string 'fixture_name' instead of the variable.

Passing request.param directly instead of the full fixture name.

The variable fixture_name holds the name of the fixture to get, so it should be passed to getfixturevalue.

3fill in blank

hard

Fix the error in the test function to use the dynamic fixture with parameterization.

PyTest

@pytest.mark.parametrize('dynamic_data', ['one', 'two'], indirect=True)
def test_dynamic(dynamic_data):
    assert isinstance(dynamic_data, list) and len(dynamic_data) == [1]

Drag options to blanks, or click blank then click option'

A1

B2

C3

D0

Attempts:

3 left

💡 Hint

Common Mistakes

Assuming the length is 2 or 1.

Using zero which would always fail.

The fixtures 'data_one' and 'data_two' return lists of length 3, so the assertion checks for length 3.

4fill in blank

hard

Fill both blanks to define two fixtures 'data_one' and 'data_two' returning different lists.

PyTest

@pytest.fixture
def data_one():
    return [1]

@pytest.fixture
def data_two():
    return [2]

Drag options to blanks, or click blank then click option'

A[1, 2, 3]

B[4, 5]

C[7, 8, 9]

D[10]

Attempts:

3 left

💡 Hint

Common Mistakes

Using the same list for both fixtures.

Choosing lists with different lengths causing test failures.

The fixtures should return different lists. 'data_one' returns [1, 2, 3] and 'data_two' returns [7, 8, 9].

5fill in blank

hard

Fill all three blanks to create a test that uses dynamic fixture selection and asserts the first element.

PyTest

@pytest.mark.parametrize('dynamic_data', ['one', 'two'], indirect=True)
def test_first_element(dynamic_data):
    assert dynamic_data[[1]] == [2] and len(dynamic_data) == [3]

Drag options to blanks, or click blank then click option'

A0

B1

C3

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 1 instead of 0 for the first element.

Incorrect length value causing assertion failure.

The first element index is 0, the first element of 'data_one' is 1, and the length of the list is 3.

Practice

1. What is the main purpose of dynamic fixture selection in pytest?

easy

A. To automatically generate test data without fixtures

B. To statically assign fixtures before running tests

C. To choose which fixture to use during test execution based on runtime conditions

D. To skip tests that use fixtures

Solution

1. Step 1: Understand fixture selection

   Dynamic fixture selection means deciding which fixture to use while the test runs, not before.

2. Step 2: Compare options

   Only To choose which fixture to use during test execution based on runtime conditions describes choosing fixtures during test execution based on conditions.

3. Final Answer:

   To choose which fixture to use during test execution based on runtime conditions -> Option C

4. Quick Check:

   Dynamic fixture selection = runtime choice [OK]

Hint: Dynamic means choosing fixtures while tests run [OK]

Common Mistakes:

• Confusing static fixture assignment with dynamic selection
• Thinking fixtures generate test data automatically
• Believing dynamic selection skips tests

2. Which of the following is the correct syntax to select a fixture dynamically inside a test using request.getfixturevalue()?

easy

A. fixture_name = request.getfixturevalue('my_fixture')

B. fixture_name = request.getfixture('my_fixture')

C. fixture_name = request.getfixturevalue(my_fixture)

D. fixture_name = request.getfixture('my_fixture')()

Solution

1. Step 1: Recall correct method name

   The method to get a fixture by name dynamically is getfixturevalue, not getfixture.

2. Step 2: Check argument type

   The fixture name must be a string, so it should be quoted.

3. Final Answer:

   fixture_name = request.getfixturevalue('my_fixture') -> Option A

4. Quick Check:

   Use getfixturevalue('fixture_name') [OK]

Hint: Use getfixturevalue with string fixture name [OK]

Common Mistakes:

• Using getfixture instead of getfixturevalue
• Passing fixture name without quotes
• Calling getfixture as a function

3. Given the code below, what will be the output when running test_dynamic_fixture?

import pytest

@pytest.fixture
def fixture_a():
    return 'A'

@pytest.fixture
def fixture_b():
    return 'B'

@pytest.mark.parametrize('use_a', [True, False])
def test_dynamic_fixture(request, use_a):
    fixture_name = 'fixture_a' if use_a else 'fixture_b'
    value = request.getfixturevalue(fixture_name)
    print(value)
    assert value in ['A', 'B']

medium

A. Prints 'A' twice and passes both tests

B. Prints 'B' then 'A' and fails one test

C. Raises an error because getfixturevalue is used incorrectly

D. Prints 'A' then 'B' and passes both tests

Solution

1. Step 1: Understand parameterization

   The test runs twice: once with use_a=True, once with use_a=False.

2. Step 2: Trace fixture selection and output

   When use_a=True, fixture_name='fixture_a' returns 'A'. When False, fixture_name='fixture_b' returns 'B'. Both print and assert succeed.

3. Final Answer:

   Prints 'A' then 'B' and passes both tests -> Option D

4. Quick Check:

   Param True->A, False->B [OK]

Hint: Param True uses fixture_a, False uses fixture_b [OK]

Common Mistakes:

• Assuming getfixturevalue causes error
• Mixing order of printed values
• Thinking test fails due to assertion

4. Identify the error in the following test code that tries to select a fixture dynamically:

import pytest

@pytest.fixture
def fix1():
    return 10

@pytest.fixture
def fix2():
    return 20

@pytest.mark.parametrize('name', ['fix1', 'fix2'])
def test_select(request, name):
    value = request.getfixture(name)
    assert value in [10, 20]

medium

A. Incorrect assert statement

B. Using request.getfixture instead of request.getfixturevalue

C. Missing parentheses when calling fixtures

D. Passing fixture name as a string instead of variable

Solution

1. Step 1: Check method name for dynamic fixture

   The correct method to get a fixture dynamically is getfixturevalue, not getfixture.

2. Step 2: Confirm usage of fixture name

   The fixture name is correctly passed as a string variable, so no issue there.

3. Final Answer:

   Using request.getfixture instead of request.getfixturevalue -> Option B

4. Quick Check:

   Use getfixturevalue, not getfixture [OK]

Hint: Remember method name: getfixturevalue, not getfixture [OK]

Common Mistakes:

• Confusing method names for fixture retrieval
• Passing fixture name incorrectly
• Misunderstanding assert logic

5. You want to write a test that uses different database connection fixtures based on an environment variable DB_TYPE. Which approach correctly implements dynamic fixture selection in pytest? A) Use request.getfixturevalue() inside the test to select the fixture by name. B) Use @pytest.mark.usefixtures() with all fixtures and skip unwanted ones. C) Use pytest_generate_tests() hook to parametrize fixtures. D) Use yield in fixtures to switch dynamically.

hard

A. Use request.getfixturevalue() inside the test to select the fixture by name.

B. Use @pytest.mark.usefixtures() with all fixtures and skip unwanted ones.

C. Use pytest_generate_tests() hook to parametrize fixtures.

D. Use yield in fixtures to switch dynamically.

Solution

1. Step 1: Understand environment-based fixture selection

   Choosing a fixture based on an environment variable requires runtime decision inside the test.

2. Step 2: Evaluate options for dynamic selection

   Use request.getfixturevalue() inside the test to select the fixture by name. uses request.getfixturevalue() to pick the fixture by name at runtime, which fits the need.

3. Step 3: Exclude other options

   Use @pytest.mark.usefixtures() with all fixtures and skip unwanted ones. applies all fixtures upfront, not dynamic. Use pytest_generate_tests() hook to parametrize fixtures. is for test parametrization, not fixture selection. Use yield in fixtures to switch dynamically. misuses yield; it does not switch fixtures dynamically.

4. Final Answer:

   Use request.getfixturevalue() inside the test to select the fixture by name. -> Option A

5. Quick Check:

   Dynamic fixture selection = getfixturevalue() [OK]

Hint: Use getfixturevalue() for runtime fixture choice [OK]

Common Mistakes:

• Trying to parametrize fixtures instead of selecting dynamically
• Using usefixtures decorator incorrectly
• Misunderstanding yield usage in fixtures