Branch coverage in PyTest - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Branch coverage with simple if-else

What is the output of the following pytest test when run with branch coverage enabled?

PyTest

def check_number(x):
    if x > 0:
        return "Positive"
    else:
        return "Non-positive"

def test_check_number():
    assert check_number(5) == "Positive"
    assert check_number(-1) == "Non-positive"

A Test passes but branch coverage is 50%

B Test passes and branch coverage is 100%

C Test fails due to assertion error

D Test passes but branch coverage is 0%

💡 Hint

Branch coverage means each branch of if-else is executed at least once.

Both branches of the if-else are tested: x=5 covers the 'if' branch, x=-1 covers the 'else' branch. So branch coverage is 100%.

❓ assertion

intermediate

Assertion to ensure full branch coverage

Which assertion in pytest ensures that both branches of this function are tested for full branch coverage?

PyTest

def is_even(n):
    if n % 2 == 0:
        return True
    else:
        return False

A assert is_even(2) and not is_even(3)

B assert is_even(2) == True

C assert is_even(3) == False

D assert is_even(0) == True

💡 Hint

To cover both branches, test both even and odd numbers.

Option A tests is_even with 2 (even) and 3 (odd), covering both branches. Other options test only one branch.

🔧 Debug

advanced

Identify missing branch coverage in test

Given this function and test, which branch is NOT covered?

PyTest

def classify_age(age):
    if age < 18:
        return "Minor"
    elif age < 65:
        return "Adult"
    else:
        return "Senior"

def test_classify_age():
    assert classify_age(10) == "Minor"
    assert classify_age(30) == "Adult"

A The 'Minor' branch is not covered

B The 'Adult' branch is not covered

C The 'Senior' branch is not covered

D All branches are covered

💡 Hint

Check which return statements are executed by the test inputs.

Test inputs cover 'Minor' and 'Adult' branches but never test age >= 65, so 'Senior' branch is not covered.

❓ framework

advanced

Using pytest-cov for branch coverage

Which pytest command correctly runs tests with branch coverage reporting?

A pytest --cov=my_module --cov-branch

B pytest --cov=my_module --branch

C pytest --coverage=my_module --branch

D pytest --cov-branch my_module

💡 Hint

The option for branch coverage is '--cov-branch' with pytest-cov.

Option A uses correct syntax: '--cov' to specify module and '--cov-branch' to enable branch coverage.

🧠 Conceptual

expert

Understanding branch coverage impact

Why is branch coverage considered a stronger metric than statement coverage in testing?

A Because branch coverage only counts executed lines, ignoring conditions

B Because branch coverage measures performance of the code during tests

C Because statement coverage requires testing all input values, branch coverage does not

D Because branch coverage ensures every possible path decision is tested, not just each line

💡 Hint

Think about what branch coverage tracks compared to statement coverage.

Branch coverage requires testing both true and false outcomes of each decision, ensuring more thorough testing than statement coverage which only checks if lines run.