Excluding code from coverage in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of coverage report with excluded code

Given the following Python code with coverage exclusion comments, what will be the total coverage percentage reported by pytest-cov?

PyTest

def add(a, b):
    return a + b

# pragma: no cover
def unused_function():
    print("This function is not covered")

result = add(2, 3)
print(result)

A 50%

B 100%

C 0%

D 75%

💡 Hint

Code marked with # pragma: no cover is excluded from coverage.

The function unused_function is excluded from coverage by the # pragma: no cover comment. Only add is counted and fully covered, so coverage is 100%.

❓ assertion

intermediate

Correct assertion for coverage exclusion

Which assertion correctly verifies that a function marked with # pragma: no cover is excluded from coverage reports?

A assert coverage_report.total_coverage < 50

B assert 'unused_function' in coverage_report.executed_functions

C assert 'unused_function' not in coverage_report.executed_functions

D assert coverage_report.total_coverage == 0

💡 Hint

Functions excluded from coverage should not appear in executed functions list.

The function marked with # pragma: no cover is not executed or counted in coverage, so it should not appear in the list of executed functions.

🔧 Debug

advanced

Why is coverage including excluded code?

Given this code snippet, coverage reports include helper_function even though it has # pragma: no cover. What is the most likely reason?

def main():
    helper_function()

# pragma: no cover
def helper_function():
    print("Helper")

main()

A The comment is misplaced; it should be above the function

B Coverage tools ignore <code># pragma: no cover</code> inside functions

C The <code># pragma: no cover</code> comment must be on the same line as the function definition

D The function is called, so it cannot be excluded

💡 Hint

Placement of exclusion comments matters for coverage tools.

The # pragma: no cover comment must be placed on the function definition line or immediately after it. Placing it below or separated causes coverage tools to ignore it.

❓ framework

advanced

Configuring pytest-cov to exclude files

Which pytest-cov configuration snippet correctly excludes all files in the tests/helpers/ directory from coverage reports?

A

[coverage:report]
omit = tests/helpers/*

B

[coverage:run]
exclude = tests/helpers/*

C

[run]
exclude = tests/helpers/*

D

[run]
omit = tests/helpers/*

💡 Hint

Check pytest-cov documentation for the correct section and key to omit files.

The omit option under the [run] section tells coverage.py which files to exclude from coverage measurement.

🧠 Conceptual

expert

Impact of excluding code on test coverage metrics

Which statement best describes the impact of excluding code with # pragma: no cover on overall test coverage metrics?

A Excluding code increases coverage percentage by removing untested code from calculation

B Excluding code decreases coverage percentage because less code is counted

C Excluding code has no effect on coverage percentage

D Excluding code causes coverage tools to report errors

💡 Hint

Think about how coverage percentage is calculated.

Excluding code removes it from the total lines counted, so coverage percentage is calculated over fewer lines, often increasing the percentage.