Cost of bugs at different stages in Testing Fundamentals - Build an Automation Script

Verify cost calculation of bugs at different development stages

Preconditions (2)

Step 1: Call calculate_bug_cost('requirements')

Step 2: Call calculate_bug_cost('design')

Step 3: Call calculate_bug_cost('development')

Step 4: Call calculate_bug_cost('testing')

Step 5: Call calculate_bug_cost('production')

Step 6: Verify the returned cost matches expected values for each stage

✅ Expected Result: The function returns correct costs: requirements=1, design=5, development=10, testing=20, production=100

Automation Requirements - pytest

Assertions Needed:

Assert returned cost equals expected cost for each stage

Best Practices:

Use parameterized tests to cover all stages

Use clear assertion messages

Keep test code simple and readable

Automated Solution

Testing Fundamentals

import pytest

def calculate_bug_cost(stage: str) -> int:
    costs = {
        'requirements': 1,
        'design': 5,
        'development': 10,
        'testing': 20,
        'production': 100
    }
    return costs.get(stage, 0)

@pytest.mark.parametrize('stage,expected_cost', [
    ('requirements', 1),
    ('design', 5),
    ('development', 10),
    ('testing', 20),
    ('production', 100)
])
def test_calculate_bug_cost(stage, expected_cost):
    cost = calculate_bug_cost(stage)
    assert cost == expected_cost, f"Cost for stage '{stage}' should be {expected_cost} but got {cost}"

This test uses pytest with parameterization to check the bug cost at each stage.

The calculate_bug_cost function returns the cost based on a dictionary lookup.

The test test_calculate_bug_cost runs once for each stage and asserts the returned cost matches the expected value.

Assertions include messages to help identify failures clearly.

Common Mistakes - 3 Pitfalls

Hardcoding test cases without parameterization

Not checking for invalid stages

Using print statements instead of assertions

Bonus Challenge

Now add data-driven testing with 3 additional invalid stage inputs and verify the cost is zero

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