Regression testing in Software Engineering - Mini Project: Build & Apply

Understanding Regression Testing

📖 Scenario: You are a QA engineer managing a regression test suite for a web application. After a code change, you need to identify affected modules, select the right tests, run them, and analyze the results to decide if the code is safe to deploy.

🎯 Goal: Build a Python model that simulates regression testing: define modules and their tests, identify affected modules from a code change, run the selected tests, and determine deployment readiness.

📋 What You'll Learn

Create a dictionary mapping modules to their test cases

Identify affected modules based on a code change

Select and run regression tests for affected modules

Determine deployment readiness based on test results

💡 Why This Matters

🌍 Real World

Regression testing is fundamental to CI/CD pipelines. Every major software company runs regression suites automatically on every commit to catch regressions before they reach production.

💼 Career

QA engineers, SDETs, and developers are expected to understand regression testing strategies, test selection, and how to analyze failures in technical interviews.

1

Define modules and their test cases

Create a dictionary called module_tests with three entries: 'auth' mapped to ['test_login', 'test_logout', 'test_token'], 'cart' mapped to ['test_add_item', 'test_remove_item'], and 'payment' mapped to ['test_checkout', 'test_refund', 'test_receipt'].

Software Engineering

# Create the module_tests dictionary
# Your code here

Hint

Each module key maps to a list of test function names that verify that module's behavior.

2

Identify affected modules

Create a list called changed_modules containing 'auth'. Create a dictionary called dependencies with 'auth' mapped to ['cart'], 'cart' mapped to ['payment'], and 'payment' mapped to an empty list []. Create an empty list called affected_modules. Use a for loop with variable module over changed_modules to append each module and its dependencies from dependencies[module] to affected_modules.

Software Engineering

module_tests = {
    'auth': ['test_login', 'test_logout', 'test_token'],
    'cart': ['test_add_item', 'test_remove_item'],
    'payment': ['test_checkout', 'test_refund', 'test_receipt']
}
# Identify affected modules from change in auth
# Your code here

Hint

When auth changes, both auth and its dependent module cart need regression testing.

3

Select and run regression tests

Create an empty list called selected_tests. Use a for loop with variable module over affected_modules to extend selected_tests with module_tests[module]. Create a dictionary called test_results. Use a for loop with variable test over selected_tests to set each test's result to 'pass' in test_results. Then override test_results['test_token'] to 'fail' to simulate a regression.

Software Engineering

module_tests = {
    'auth': ['test_login', 'test_logout', 'test_token'],
    'cart': ['test_add_item', 'test_remove_item'],
    'payment': ['test_checkout', 'test_refund', 'test_receipt']
}
changed_modules = ['auth']
dependencies = {
    'auth': ['cart'],
    'cart': ['payment'],
    'payment': []
}
affected_modules = []
for module in changed_modules:
    affected_modules.append(module)
    affected_modules.extend(dependencies[module])
# Select tests, run them, and simulate one failure
# Your code here

Hint

Collect all tests for affected modules, run them all as pass, then override one to simulate a failure.

4

Determine deployment readiness

Create a list called failures using a list comprehension that collects each test from test_results where test_results[test] equals 'fail'. Create a variable deploy_ready set to len(failures) == 0.

Software Engineering

module_tests = {
    'auth': ['test_login', 'test_logout', 'test_token'],
    'cart': ['test_add_item', 'test_remove_item'],
    'payment': ['test_checkout', 'test_refund', 'test_receipt']
}
changed_modules = ['auth']
dependencies = {
    'auth': ['cart'],
    'cart': ['payment'],
    'payment': []
}
affected_modules = []
for module in changed_modules:
    affected_modules.append(module)
    affected_modules.extend(dependencies[module])
selected_tests = []
for module in affected_modules:
    selected_tests.extend(module_tests[module])
test_results = {}
for test in selected_tests:
    test_results[test] = 'pass'
test_results['test_token'] = 'fail'
# Determine failures and deployment readiness
# Your code here

Hint

If any test failed, the code is not ready to deploy. deploy_ready should be False when failures exist.