Coverage in CI pipelines in PyTest - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is code coverage in the context of CI pipelines?

Code coverage measures how much of your code is tested by automated tests during CI runs. It helps ensure tests cover important parts of the code.

beginner

Why integrate coverage reports in CI pipelines?

Integrating coverage reports in CI helps catch untested code early, improves code quality, and prevents bugs by enforcing testing standards automatically.

beginner

Which pytest plugin is commonly used to measure coverage?

The pytest-cov plugin is used to measure code coverage when running pytest tests. It generates coverage reports in various formats.

intermediate

How can you fail a CI build if coverage drops below a threshold using pytest?

Use pytest-cov options like --cov-fail-under=80 to fail the build if coverage is below 80%. This enforces minimum coverage standards automatically.

intermediate

What is a common format for coverage reports to integrate with CI tools?

The XML format (coverage.xml) is commonly used because many CI tools and coverage services can read it to display coverage results.

What does code coverage measure in CI pipelines?

A The percentage of code executed by tests

B The number of tests written

C The speed of test execution

D The number of bugs found

Code coverage measures how much of the code is executed by automated tests during CI runs.

Which pytest plugin helps generate coverage reports?

A pytest-xdist

B pytest-mock

C pytest-html

D pytest-cov

pytest-cov is the plugin used to measure and report code coverage.

How can you make a CI build fail if coverage is too low?

A Use --max-time option with pytest

B Use --fail-on-error option with pytest

C Use --cov-fail-under option with pytest-cov

D Use --skip-covered option with pytest-cov

The --cov-fail-under option sets a minimum coverage threshold that fails the build if not met.

Which coverage report format is widely supported by CI tools?

A XML

B TXT

C CSV

D JSON

XML format (coverage.xml) is commonly used for integration with CI tools and coverage services.

Why is it important to include coverage in CI pipelines?

A To speed up the build process

B To ensure tests cover critical code and maintain quality

C To reduce the number of tests

D To avoid writing tests

Coverage helps ensure tests cover important code, improving quality and catching bugs early.

Explain how to set up pytest coverage reporting in a CI pipeline.

Think about the commands and CI configuration steps.

Describe the benefits of enforcing coverage thresholds in CI pipelines.

Consider quality and team discipline reasons.

Practice

1. What is the main purpose of using coverage tools like pytest --cov in CI pipelines?

easy

A. To generate user documentation

B. To speed up the test execution time

C. To deploy the application automatically

D. To measure how much of the code is tested automatically

Solution

1. Step 1: Understand coverage tools in testing

   Coverage tools measure the percentage of code executed by tests.

2. Step 2: Role in CI pipelines

   In CI, coverage helps ensure tests cover enough code to catch bugs early.

3. Final Answer:

   To measure how much of the code is tested automatically -> Option D

4. Quick Check:

   Coverage measures tested code = D [OK]

Hint: Coverage shows tested code percentage in CI [OK]

Common Mistakes:

• Confusing coverage with test speed
• Thinking coverage deploys code
• Assuming coverage creates docs

2. Which of the following is the correct command to run pytest with coverage reporting?

easy

A. pytest --cov=.

B. pytest --cov-report=html --cov

C. pytest -coverage

D. pytest --coverage=report

Solution

1. Step 1: Identify correct pytest coverage syntax

   The correct syntax uses --cov to specify coverage on the current directory.

2. Step 2: Analyze options

   pytest --cov=. correctly runs coverage on the current directory with default terminal reporting.

3. Final Answer:

   pytest --cov=. -> Option A

4. Quick Check:

   Correct pytest coverage command = B [OK]

Hint: Use --cov and --cov-report together for coverage output [OK]

Common Mistakes:

• Using incorrect flags like --coverage=report
• Missing --cov option
• Wrong flag syntax like -coverage

3. Given this pytest command in a CI pipeline:

pytest --cov=myapp --cov-report=term

What will be the output shown in the CI logs?

medium

A. A summary of coverage percentages printed in the terminal

B. No coverage information will be shown

C. A detailed HTML coverage report saved to disk

D. An error because --cov-report=term is invalid

Solution

1. Step 1: Understand --cov-report=term option

   The term option prints coverage summary in the terminal output.

2. Step 2: Analyze expected CI log output

   The CI logs will show coverage percentages summary, not an HTML file or error.

3. Final Answer:

   A summary of coverage percentages printed in the terminal -> Option A

4. Quick Check:

   --cov-report=term shows summary in terminal = C [OK]

Hint: term report prints coverage summary in console [OK]

Common Mistakes:

• Expecting HTML report in terminal
• Assuming no coverage output
• Thinking --cov-report=term is invalid

4. You added coverage to your CI pipeline with this command:

pytest --cov=myapp --cov-report=html

But the coverage report is missing after the run. What is the most likely cause?

medium

A. The --cov option is misspelled

B. The coverage report is saved in a different directory, not checked by CI

C. pytest does not support coverage reporting

D. The tests did not run because of a syntax error

Solution

1. Step 1: Understand where coverage HTML reports are saved

   By default, HTML reports are saved in a folder named htmlcov in the current directory.

2. Step 2: Check CI pipeline file handling

   If the CI pipeline does not collect or upload this folder, the report will appear missing.

3. Final Answer:

   The coverage report is saved in a different directory, not checked by CI -> Option B

4. Quick Check:

   HTML report saved in htmlcov folder = A [OK]

Hint: Check htmlcov folder location in CI artifacts [OK]

Common Mistakes:

• Assuming --cov is misspelled without checking
• Believing pytest lacks coverage support
• Ignoring test run errors

5. In a CI pipeline, you want to fail the build if coverage falls below 80%. Which pytest coverage option helps enforce this?

hard

A. --fail-if-coverage-below=80

B. --coverage-threshold=80

C. --cov-fail-under=80

D. --cov-minimum=80

Solution

1. Step 1: Identify pytest coverage option for minimum coverage

   The correct option is --cov-fail-under which sets a minimum coverage percentage.

2. Step 2: Understand CI build failure behavior

   If coverage is below the set value, pytest returns a failure status causing CI to fail the build.

3. Final Answer:

   --cov-fail-under=80 -> Option C

4. Quick Check:

   Fail build if coverage under 80% = B [OK]

Hint: Use --cov-fail-under to enforce coverage minimum [OK]

Common Mistakes:

• Using incorrect or non-existent flags
• Confusing coverage reporting with build failure
• Assuming coverage threshold is set elsewhere