pytest-cov for coverage - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Understanding pytest-cov output summary

You run pytest with pytest-cov on a project with 3 Python files. The coverage report shows 85% coverage overall. What does this mean?

A 85% of all lines in the 3 files were executed during tests

B 85% of the tests passed successfully

C 85% of the functions in the project have tests

D 85% of the test files were run by pytest

💡 Hint

Coverage measures how much code was run by tests, not test pass rate.

pytest-cov measures how many lines of code were executed during tests. 85% coverage means 85% of all lines in the files ran at least once.

❓ assertion

intermediate

Correct assertion to check coverage threshold

You want your pytest-cov to fail tests if coverage is below 90%. Which assertion in your pytest test is correct?

A assert coverage_percent > 90

B assert coverage_percent >= 90

C assert coverage_percent == 90

D assert coverage_percent <= 90

💡 Hint

You want to allow 90% or more coverage, not just exactly 90%.

The assertion should check coverage is at least 90%, so using >= 90 is correct.

🔧 Debug

advanced

Why does pytest-cov report 0% coverage?

You run pytest --cov=myapp tests/ but the coverage report shows 0% coverage. What is the most likely cause?

A The tests folder is empty

B pytest-cov is not installed correctly

C The <code>myapp</code> package is not imported or used in tests

D The coverage report file is corrupted

💡 Hint

Coverage measures executed code. If code is never run, coverage is zero.

If the tested package is not imported or run during tests, coverage will be zero because no code was executed.

❓ framework

advanced

Configuring pytest-cov to generate HTML report

Which pytest command correctly runs tests with coverage and generates an HTML coverage report in the htmlcov folder?

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

B pytest --cov=myapp --html=htmlcov

C pytest --coverage=myapp --report=htmlcov

D pytest --cov-report=html --cov=myapp --output=htmlcov

💡 Hint

The option for HTML report is --cov-report=html.

The correct syntax is --cov-report=html to generate an HTML report in the default htmlcov folder.

🧠 Conceptual

expert

Interpreting branch coverage in pytest-cov

pytest-cov shows 75% branch coverage but 90% line coverage. What does this difference mean?

A Branch coverage counts test cases, line coverage counts lines

B Only 75% of lines were executed, but 90% of branches were tested

C Branch coverage is always lower than line coverage by definition

D Some decision points (if/else) were not fully tested, even though most lines ran

💡 Hint

Branch coverage checks if all possible paths in decisions ran.

Branch coverage measures if all possible paths in code decisions were tested. 75% means some if/else paths were missed, even if 90% of lines ran.