Automation ROI calculation in Testing Fundamentals - Build an Automation Script

Calculate Automation ROI for a Test Suite

Preconditions (5)

Step 1: Collect manual test execution time per test case in hours

Step 2: Collect automated test execution time per test case in hours

Step 3: Collect manual test maintenance time per test case in hours

Step 4: Collect automated test maintenance time per test case in hours

Step 5: Collect number of test executions planned

Step 6: Calculate total manual time = (manual execution time + manual maintenance time) * number of executions

Step 7: Calculate total automated time = (automated execution time + automated maintenance time) * number of executions

Step 8: Calculate time saved = total manual time - total automated time

Step 9: Calculate ROI percentage = (time saved / total automated time) * 100

Step 10: Verify ROI percentage is greater than 0

✅ Expected Result: The ROI percentage is calculated correctly and is greater than 0, indicating automation saves time.

Automation Requirements - Python unittest

Assertions Needed:

Assert ROI percentage is a float

Assert ROI percentage is greater than 0

Best Practices:

Use functions to separate calculation logic

Use clear variable names

Use unittest assertions for validation

Handle division by zero if automated time is zero

Automated Solution

Testing Fundamentals

import unittest


def calculate_roi(manual_exec, manual_maint, auto_exec, auto_maint, executions):
    total_manual = (manual_exec + manual_maint) * executions
    total_auto = (auto_exec + auto_maint) * executions
    if total_auto == 0:
        raise ValueError("Automated total time cannot be zero")
    time_saved = total_manual - total_auto
    roi = (time_saved / total_auto) * 100
    return roi


class TestAutomationROICalculation(unittest.TestCase):
    def test_roi_calculation(self):
        manual_exec = 2.0  # hours
        manual_maint = 0.5  # hours
        auto_exec = 0.5  # hours
        auto_maint = 0.2  # hours
        executions = 10

        roi = calculate_roi(manual_exec, manual_maint, auto_exec, auto_maint, executions)

        self.assertIsInstance(roi, float, "ROI should be a float")
        self.assertGreater(roi, 0, "ROI should be greater than 0")

    def test_zero_automated_time(self):
        with self.assertRaises(ValueError):
            calculate_roi(1, 1, 0, 0, 5)


if __name__ == '__main__':
    unittest.main()

The calculate_roi function computes the return on investment percentage by first calculating total manual and automated times, then computing the time saved and ROI percentage. It raises an error if automated total time is zero to avoid division by zero.

The TestAutomationROICalculation class uses Python's unittest framework to test the ROI calculation. It checks that the ROI is a float and greater than zero, matching the expected result. It also tests that the function raises an error when automated time is zero.

This structure separates calculation logic from tests, uses clear variable names, and applies proper assertions for validation.

Common Mistakes - 4 Pitfalls

Not handling division by zero when automated time is zero

{'mistake': "Using unclear variable names like 'a', 'b', 'c'", 'why_bad': 'Makes code hard to read and understand.', 'correct_approach': 'Use descriptive names like manual_exec, auto_maint, executions.'}

Not using assertions to check ROI type and value

Mixing calculation logic inside test methods

Bonus Challenge

Now add data-driven testing with 3 different sets of inputs for manual and automated times and executions.

Show Hint