Module-Level Unit Testing Quiz Quiz

Explore the core concepts and best practices of module-level unit testing, including test isolation, mocking techniques, and code coverage. This quiz is designed to assess your understanding of unit testing at the module granularity, helping reinforce effective software testing strategies.

1. Scope of Module-Level Unit Tests

   Which of the following best describes the primary focus of module-level unit testing in software development?

   1. Checking the performance of the whole application under heavy load
   2. Verifying the internal logic of a specific module in isolation from other modules
   3. Ensuring that user interface elements render consistently
   4. Testing the integration between several unrelated modules

   Explanation: Module-level unit tests are designed to validate the internal logic and behavior of a single module, making sure it functions correctly without interference from other modules. Testing integration between modules is not the purpose of unit tests but rather integration tests. Performance testing and UI rendering focus on different aspects like system efficiency and user experience, which are outside the scope of module-level unit testing.

2. Test Isolation Techniques

   If a module depends on external services, what is the most appropriate method to ensure unit tests for that module remain fast and isolated?

   1. Using mocking to simulate the external services
   2. Calling the actual external services each time a test runs
   3. Increasing the network timeout limit for service calls
   4. Skipping tests that rely on external data

   Explanation: Mocking allows developers to simulate external services, ensuring unit tests are fast, reliable, and independent of factors outside the module. Calling real services can make tests slow and flaky. Increasing timeout limits does not solve the core issue of dependency. Skipping tests undermines coverage and reliability, so mocking remains the most appropriate solution.

3. Code Coverage Meaning

   Which statement correctly interprets a module’s code coverage report indicating 85% function coverage?

   1. Eighty-five percent of external dependencies have been removed
   2. Eighty-five percent of test cases have passed
   3. Eighty-five percent of the module’s code lines are error-free
   4. Eighty-five percent of the module’s functions are executed by at least one test case

   Explanation: Function coverage shows the fraction of defined functions that have been executed during testing. It does not measure code correctness or absence of errors, only execution. The report does not relate to the removal of dependencies or test pass rates. Therefore, it specifically refers to how many module functions are exercised by the unit tests.

4. Refactoring and Unit Tests

   After refactoring internal logic within a module without changing its input or output, what is the expected impact on well-designed unit tests?

   1. The existing unit tests should still pass without modification
   2. The module will be automatically excluded from further testing
   3. The tests will require code changes to match the new logic
   4. The tests will fail because their dependencies are outdated

   Explanation: Well-designed unit tests focus on validating input-output behavior, not internal implementation. If the external interface remains unchanged, the tests should continue passing. Changing the test code or worrying about outdated dependencies is unnecessary when only internal logic is refactored. There is also no automatic exclusion from testing after refactoring.

5. Choosing What to Test

   When creating unit tests at the module level, which functions should typically be the main focus?

   1. Debugging utilities unused in production
   2. Public functions that form the module’s interface
   3. Private helper functions used internally
   4. Test functions from other modules

   Explanation: Unit tests at the module level are most effective when they target public functions, since these define the module’s external behavior. Testing private helpers can lead to brittle and tightly-coupled tests, while debugging utilities or other modules’ test functions are irrelevant for validating the module's correctness. Focusing on the interface ensures stable and meaningful tests.