Worker distribution strategies in PyTest - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to run tests in parallel using pytest's xdist plugin.

PyTest

pytest.main(['-n', '[1]'])

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

A4

B2

C0

D1

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 disables parallelism, so tests run sequentially.

Using 1 is effectively the same as no parallelism.

Using '-n 2' tells pytest to run tests using 2 workers in parallel.

2fill in blank

medium

Complete the code to distribute tests by module using pytest xdist.

PyTest

pytest.main(['-n', '3', '--dist=[1]'])

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

Aloadscope

Bno

Cloadfile

Deach

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'no' disables distribution, so tests run sequentially.

Using 'loadscope' distributes by scope, not by file.

The '--dist=loadfile' option distributes tests by file, running all tests in a file on the same worker.

3fill in blank

hard

Fix the error in the pytest command to enable loadscope distribution with 4 workers.

PyTest

pytest.main(['-n', '[1]', '--dist=loadscope'])

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

A4

B0

Cone

D-4

Attempts:

3 left

💡 Hint

Common Mistakes

Using 0 disables parallelism.

Using negative numbers or strings causes errors.

The number of workers must be a positive integer. '4' correctly sets 4 workers.

4fill in blank

hard

Fill both blanks to configure pytest to run 3 workers and distribute tests by scope.

PyTest

pytest.main(['-n', '[1]', '--dist=[2]'])

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

A3

Bloadfile

Cloadscope

Dno

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'no' disables distribution.

Mixing worker count and distribution strategy incorrectly.

Using '-n 3' runs 3 workers, and '--dist=loadscope' distributes tests by their scope.

5fill in blank

hard

Fill all three blanks to run pytest with 5 workers, distribute by file, and enable boxed mode.

PyTest

pytest.main(['-n', '[1]', '--dist=[2]', '[3]'])

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

A4

B5

Cloadfile

D--boxed

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong worker count numbers.

Confusing distribution strategies.

Forgetting to enable boxed mode correctly.

Using '-n 5' runs 5 workers, '--dist=loadfile' distributes tests by file, and '--boxed' runs tests in isolated subprocesses.

Practice

1. What does the --dist=loadscope option do in pytest-xdist worker distribution?

easy

A. It distributes tests randomly to all workers.

B. It runs all tests sequentially on a single worker.

C. It groups tests by their scope and distributes them to workers.

D. It groups tests by file size before distribution.

Solution

1. Step 1: Understand the meaning of loadscope

   The loadscope mode groups tests by their scope, such as class or module, so related tests run together.

2. Step 2: Compare with other distribution modes

   Unlike random or file-based grouping, loadscope keeps related tests together for better caching and setup reuse.

3. Final Answer:

   It groups tests by their scope and distributes them to workers. -> Option C

4. Quick Check:

   loadscope = group by scope [OK]

Hint: Loadscope groups tests by scope like class or module [OK]

Common Mistakes:

• Confusing loadscope with random distribution
• Thinking loadscope groups by file size
• Assuming loadscope runs tests sequentially

2. Which of the following is the correct pytest command to run tests with 4 workers using file-based distribution?

easy

A. pytest -n 4 --dist=loadfile

B. pytest --dist=loadfile -n four

C. pytest -n=4 --dist=loadscope

D. pytest -n 4 --dist=loadgroup

Solution

1. Step 1: Identify correct syntax for number of workers

   The correct syntax is -n 4 to specify 4 workers; spelling out 'four' is invalid.

2. Step 2: Match distribution mode to file-based

   The file-based distribution mode is loadfile, so --dist=loadfile is correct.

3. Final Answer:

   pytest -n 4 --dist=loadfile -> Option A

4. Quick Check:

   -n 4 and --dist=loadfile correct syntax [OK]

Hint: Use -n number and --dist=loadfile for file grouping [OK]

Common Mistakes:

• Using spelled-out numbers like 'four'
• Mixing distribution modes incorrectly
• Using equals sign with -n option

3. Given this pytest command: pytest -n 3 --dist=loadfile, and three test files test_a.py, test_b.py, test_c.py, how will tests be distributed?

medium

A. Tests run sequentially on a single worker.

B. All workers run tests from all files randomly.

C. Tests are grouped by class across files.

D. Each worker runs tests from one file exclusively.

Solution

1. Step 1: Understand loadfile distribution

   Loadfile mode assigns tests grouped by file to different workers, so each worker gets whole files.

2. Step 2: Match number of workers to files

   With 3 workers and 3 files, each worker will get one file's tests exclusively.

3. Final Answer:

   Each worker runs tests from one file exclusively. -> Option D

4. Quick Check:

   loadfile = group by file [OK]

Hint: Loadfile means one file per worker [OK]

Common Mistakes:

• Thinking tests are split randomly
• Confusing loadfile with loadscope
• Assuming tests run sequentially

4. You run pytest -n 2 --dist=loadscope but notice tests from the same class run on different workers. What is the likely cause?

medium

A. Tests are not properly grouped because the class scope is not detected.

B. The -n option must be set to 1 for loadscope.

C. The --dist option is ignored when using multiple workers.

D. Tests are always distributed randomly regardless of options.

Solution

1. Step 1: Understand loadscope grouping behavior

   Loadscope groups tests by scope like class or module, so tests in the same class should run together.

2. Step 2: Identify why grouping fails

   If tests from the same class run on different workers, pytest likely failed to detect the class scope properly, causing wrong grouping.

3. Final Answer:

   Tests are not properly grouped because the class scope is not detected. -> Option A

4. Quick Check:

   Undetected scope breaks loadscope grouping [OK]

Hint: Undetected scope causes loadscope to fail grouping [OK]

Common Mistakes:

• Thinking -n must be 1 for loadscope
• Believing --dist is ignored with multiple workers
• Assuming distribution is always random

5. You want to run tests in custom groups using pytest-xdist. Which command and option combination allows you to define and use custom test groups for worker distribution?

hard

A. pytest -n 3 --dist=loadgroup --tx group1 --tx group2 --tx group3

B. pytest -n 3 --dist=loadgroup

C. pytest -n 3 --dist=loadfile --group=custom

D. pytest -n 3 --dist=loadscope --group=custom

Solution

1. Step 1: Identify the distribution mode for custom groups

   The loadgroup mode is designed for custom grouping of tests for distribution.

2. Step 2: Understand correct command usage

   Using --dist=loadgroup with -n 3 enables pytest-xdist to distribute tests based on user-defined groups configured elsewhere (e.g., in pytest hooks).

3. Final Answer:

   pytest -n 3 --dist=loadgroup -> Option B

4. Quick Check:

   loadgroup enables custom test groups [OK]

Hint: Use --dist=loadgroup to enable custom test groups [OK]

Common Mistakes:

• Adding invalid --group option
• Using --tx incorrectly for grouping
• Confusing loadgroup with loadfile or loadscope