Test Coverage and Security Aspects in TDD Quiz

Explore core principles of test coverage and code quality in Test-Driven Development with a focus on security testing practices. This quiz evaluates your understanding of TDD processes, code coverage strategies, and how secure coding benefits from test-driven methods.

1. Coverage Metrics in TDD

   Which coverage metric best helps assess whether all critical security branches in a TDD-managed codebase have been tested?

   1. Branch coverage
   2. Line coverage
   3. Function count
   4. Module imports

   Explanation: Branch coverage tracks which branches of conditional statements are tested, making it effective for ensuring that all possible paths, including security-relevant ones, are exercised. Line coverage only measures which lines were executed, missing logical branches. Function count does not provide information about the completeness of security path testing. Module imports relate merely to code organization, not test thoroughness.

2. Security Test Example in TDD

   During TDD, a developer writes a failing test where user input includes SQL code; what is the likely security goal of this test?

   1. Preventing SQL injection
   2. Increasing code speed
   3. Checking variable renaming
   4. Measuring database size

   Explanation: Writing a test to handle user input that includes SQL is a direct method to catch and prevent SQL injection vulnerabilities, which are common security issues. Increasing code speed is unrelated to handling input safely. Variable renaming pertains to code maintenance, not security. Measuring database size is a performance or scaling metric, not a security concern.

3. Iterative Development and Security

   How does iterative TDD improve the security of a codebase compared to ad-hoc testing approaches?

   1. By continuously integrating tests for each feature
   2. By writing all security tests after deployment
   3. By only reviewing requirements at project start
   4. By ignoring failed tests to save time

   Explanation: TDD ensures that with each new feature or change, relevant tests—including those for security—are created and integrated, enabling early and consistent detection of vulnerabilities. Post-deployment test writing (option B) misses vulnerabilities before release. Reviewing requirements at the start without ongoing checks does not address emerging security risks. Ignoring failed tests undermines both quality and security.

4. Test Suite Quality in Security Testing

   What can frequent false positives in a TDD-powered security test suite indicate?

   1. Test cases lack precision in defining real threats
   2. There are no security issues in the codebase
   3. Test execution speed is always optimal
   4. High test coverage is achieved

   Explanation: Frequent false positives point to imprecise test design, as tests may flag non-issues as threats, reducing trust in the suite. It doesn't mean that there are no actual security issues (option B); real vulnerabilities might still exist. Test execution speed (option C) isn't necessarily linked to precision of test results. High coverage (option D) could still coexist with poor test quality.

5. Limitations of Test Coverage

   Why is 100% test coverage not a guarantee against security vulnerabilities in TDD workflows?

   1. Tests may not cover all threat scenarios
   2. All tested code is automatically secure
   3. Coverage always implies code correctness
   4. Coverage eliminates human error

   Explanation: Even at 100% coverage, tests might miss certain threat vectors or scenarios, which leaves security gaps. Having all code tested (option B) does not mean it is free of security flaws. Coverage as a metric (option C) doesn't guarantee code correctness or security. Human error and unforeseen risks (option D) can still occur despite high coverage.