pytest-cov setup - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is pytest-cov used for?

pytest-cov is a plugin for pytest that measures code coverage during test runs. It shows which parts of your code were tested and which were not.

beginner

How do you install pytest-cov?

You install pytest-cov using pip with the command: pip install pytest-cov.

beginner

How do you run pytest with coverage reporting?

Run tests with coverage by using: pytest --cov=your_package_name. Replace your_package_name with the folder or module you want to check coverage for.

intermediate

What does the option --cov-report=term do?

It shows the coverage report directly in the terminal after tests finish, so you can quickly see which lines were covered.

intermediate

How can you generate an HTML coverage report with pytest-cov?

Use the command: pytest --cov=your_package_name --cov-report=html. This creates a folder named htmlcov with a detailed, easy-to-read coverage report you can open in a browser.

Which command installs pytest-cov?

A pytest --install-cov

B pip install pytest-cov

C pip install coverage

D pip install pytest

The correct command to install pytest-cov is pip install pytest-cov.

What does pytest --cov=myapp do?

A Runs tests only for the 'myapp' package

B Generates an HTML report only

C Runs tests and measures coverage for the 'myapp' package

D Installs coverage for 'myapp'

This command runs all tests and measures how much of 'myapp' code is covered by tests.

How do you see coverage results in the terminal?

A Coverage is shown by default

B Add <code>--show-coverage</code> option

C Add <code>--coverage-output=console</code> option

D Add <code>--cov-report=term</code> option

Use --cov-report=term to display coverage results in the terminal.

Where does pytest-cov put the HTML report by default?

A In the <code>htmlcov</code> folder

B In the root folder

C In the <code>coverage</code> folder

D In the <code>reports</code> folder

The HTML coverage report is saved in the htmlcov folder by default.

What must you specify to measure coverage for a specific package?

A The package name after <code>--cov=</code>

B The test file name

C The Python version

D The pytest version

You specify the package or folder name after --cov= to measure coverage for it.

Explain how to set up pytest-cov to measure and report test coverage for a Python project.

Think about installation, running tests, and viewing coverage.

Describe the benefits of using pytest-cov in your testing workflow.

Consider how coverage helps improve tests.

Practice

1. What is the main purpose of using pytest-cov in testing?

easy

A. To speed up test execution time

B. To measure how much of your code is tested by your tests

C. To automatically fix failing tests

D. To generate test data automatically

Solution

1. Step 1: Recall pytest-cov's core function

   pytest-cov is a plugin that tracks which parts of your code are executed during tests.

2. Step 2: Eliminate incorrect options

   Only To measure how much of your code is tested by your tests correctly describes coverage measurement, others describe unrelated features.

3. Final Answer:

   To measure how much of your code is tested by your tests -> Option B

4. Quick Check:

   pytest-cov measures coverage = A [OK]

Hint: Remember: cov means coverage, it shows tested code parts [OK]

Common Mistakes:

• Confusing coverage with test speed
• Thinking pytest-cov fixes tests
• Assuming it generates test data

2. Which command correctly installs the pytest-cov plugin?

easy

A. pip install pytest-cov

B. pip install pytest_cov

C. pip install pytestcov

D. pip install pytest coverage

Solution

1. Step 1: Recall the exact package name

   The official package name is 'pytest-cov' with a hyphen.

2. Step 2: Compare options with correct spelling

   Only pip install pytest-cov matches the correct package name and syntax.

3. Final Answer:

   pip install pytest-cov -> Option A

4. Quick Check:

   Correct package name = B [OK]

Hint: Use hyphen, not underscore or spaces in package name [OK]

Common Mistakes:

• Using underscore instead of hyphen
• Adding spaces in package name
• Misspelling the package name

3. What will be the output when running pytest --cov=my_module if all code in my_module is covered by tests?

medium

A. Tests will fail automatically

B. An error saying coverage data not found

C. No coverage report is shown

D. A coverage report showing 100% coverage for my_module

Solution

1. Step 1: Analyze the pytest --cov command

   The command runs tests and measures coverage for 'my_module'.

2. Step 2: Determine output for 100% coverage

   If all code is tested, coverage report shows 100% coverage.

3. Final Answer:

   A coverage report showing 100% coverage for my_module -> Option D

4. Quick Check:

   Full coverage means 100% report = A [OK]

Hint: Full coverage means report shows 100% coverage [OK]

Common Mistakes:

• Expecting errors when coverage is full
• Thinking coverage report is hidden by default
• Assuming tests fail if coverage is 100%

4. You run pytest --cov=my_module --cov-report=html but no HTML report is generated. What is the most likely cause?

medium

A. You forgot to install pytest-cov plugin

B. You did not specify the module name correctly

C. The HTML report is generated in a different folder

D. The tests did not run at all

Solution

1. Step 1: Check common reasons for missing HTML report

   pytest-cov generates HTML reports in a folder named 'htmlcov' by default.

2. Step 2: Understand report location

   The report is generated but may be in a folder you did not check.

3. Final Answer:

   The HTML report is generated in a different folder -> Option C

4. Quick Check:

   HTML report folder = C [OK]

Hint: Check 'htmlcov' folder for HTML report after running tests [OK]

Common Mistakes:

• Assuming plugin is not installed without checking
• Thinking report is shown in terminal only
• Believing tests must fail to generate report

5. You want to measure coverage for multiple modules mod1 and mod2 and generate both terminal and HTML reports. Which command is correct?

hard

A. pytest --cov=mod1,mod2 --cov-report=term --cov-report=html

B. pytest --cov=mod1 --cov-report=term --cov=mod2 --cov-report=term

C. pytest --cov=mod1 mod2 --cov-report=term,html

D. pytest --cov=mod1 --cov=mod2 --cov-report=term --cov-report=term

Solution

1. Step 1: Understand multiple module coverage syntax

   pytest-cov accepts multiple modules separated by commas in a single --cov option.

2. Step 2: Understand multiple report formats syntax

   Multiple reports are specified by repeating the --cov-report flag, e.g., --cov-report=term --cov-report=html.

3. Final Answer:

   pytest --cov=mod1,mod2 --cov-report=term --cov-report=html -> Option A

4. Quick Check:

   Comma for modules, repeat --cov-report = D [OK]

Hint: Use commas to list modules in one --cov option [OK]

Common Mistakes:

• Using multiple --cov options instead of comma separation
• Combining modules without commas
• Incorrectly combining report types in one option