Coverage thresholds in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

What is the test result with coverage threshold set to 80%?

Given the following pytest coverage configuration, what will be the test execution result if the actual coverage is 75%?

PyTest

[run]
branch = True

[report]
fail_under = 80

[paths]
source = src

# Assume tests run and coverage measured at 75%

A Tests pass, coverage report shows 75%

B Tests pass but warning about coverage below threshold

C Tests fail due to syntax error in config

D Tests fail due to coverage below 80%

💡 Hint

Coverage fail_under sets minimum coverage percentage to pass tests.

The fail_under setting enforces a minimum coverage percentage. If actual coverage is below 80%, tests fail.

❓ assertion

intermediate

Which assertion correctly checks coverage threshold in pytest?

You want to assert that coverage is at least 90% in a pytest test. Which assertion is correct?

PyTest

def test_coverage(coverage_percent):
    # coverage_percent is a float representing coverage %

A assert coverage_percent > 90

B assert coverage_percent >= 90

C assert coverage_percent == 90

D assert coverage_percent <= 90

💡 Hint

Threshold means coverage must be equal or greater than the set value.

Using >= 90 ensures coverage is at least 90%, matching threshold requirements.

🔧 Debug

advanced

Why does coverage threshold fail even though coverage is 85%?

You set fail_under=85 in your coverage config but tests fail with coverage 85%. What is the likely cause?

PyTest

[report]
fail_under = 85

# Actual coverage measured: 85.0%

A fail_under requires coverage greater or equal to 85%, so failure is unexpected

B fail_under requires coverage strictly greater than 85%

C fail_under is ignored if branch coverage is enabled

D fail_under requires coverage less than 85%

💡 Hint

Check if fail_under is inclusive or exclusive of the threshold value.

fail_under fails the build only if coverage < 85%. Coverage of 85% (>=85%) should pass, so failure is unexpected (e.g., due to floating-point precision, branch coverage, or per-file thresholds).

🧠 Conceptual

advanced

What is the purpose of coverage thresholds in testing?

Why do teams use coverage thresholds in their test suites?

A To ensure a minimum percentage of code is tested to maintain quality

B To guarantee tests run faster by skipping untested code

C To automatically fix uncovered code during tests

D To disable tests if coverage is too high

💡 Hint

Think about quality control in testing.

Coverage thresholds enforce a minimum tested code percentage, helping maintain code quality.

❓ framework

expert

How to configure pytest-cov to fail tests if coverage is below 75%?

Which pytest command line option correctly enforces a 75% coverage threshold that fails tests if not met?

A pytest --cov=src --fail-under=75

B pytest --coverage=src --fail-under=75

C pytest --cov=src --cov-fail-under=75

D pytest --cov=src --cov-fail-over=75

💡 Hint

Check pytest-cov documentation for correct flag names.

The correct flag is --cov-fail-under to set minimum coverage threshold.