Conditional parametrize in PyTest - Build an Automation Script

Test addition function with conditional parameters

Preconditions (2)

Step 1: Create a test function that adds two numbers

Step 2: Use pytest parametrize to test multiple input pairs

Step 3: Add a condition to skip some parameters based on a flag

Step 4: Run the tests

Step 5: Verify that only the parameters meeting the condition are tested

✅ Expected Result: Tests run only for the parameters that meet the condition, others are skipped or not run

Automation Requirements - pytest

Assertions Needed:

Verify the addition result is correct for each parameter set

Verify tests are skipped or not run for parameters failing the condition

Best Practices:

Use @pytest.mark.parametrize with a conditional filter

Use clear test names for each parameter set

Avoid hardcoding test data inside the test function

Use pytest skip markers or conditional logic inside parametrize

Automated Solution

PyTest

import pytest

# Flag to control which parameters to test
run_extended_tests = False

# Define test data with a condition
params = [
    (1, 2, 3, True),    # (a, b, expected, run_test)
    (3, 5, 8, True),
    (10, 20, 30, False),
    (0, 0, 0, True)
]

# Filter parameters based on the flag
filtered_params = [ (a, b, expected) for a, b, expected, run_test in params if run_test or run_extended_tests ]

@pytest.mark.parametrize("a,b,expected", filtered_params)
def test_addition(a, b, expected):
    assert a + b == expected

This test script uses pytest.mark.parametrize to run the test_addition function with multiple sets of inputs.

The params list includes a boolean flag run_test to indicate if the test case should run by default.

The filtered_params list comprehension filters the parameters based on the run_extended_tests flag. If run_extended_tests is False, only parameters with run_test=True are included.

This way, you can control which test cases run conditionally without changing the test code.

The assertion checks that the sum of a and b equals the expected result.

Common Mistakes - 3 Pitfalls

Hardcoding all parameters without condition

Using if statements inside the test function to skip tests

Not providing descriptive test ids for parameters

Bonus Challenge

Add data-driven testing with 3 different input sets and a condition to run only even sums

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