CSCI 370 Lec 20: Software Testing and Testable Software

Regression Testing

• Definition: Bugs in software that were fixed reappear.
• Process:
  1. Identify the bug.
  2. Fix the bug.
  3. Create a test for the bug.
  4. Continuously run the test to ensure the bug does not return.
• Tools: Automated testing software is often used to simplify this process.

Test-Driven Development (TDD)

• Definition: Write tests before writing the code.
• Steps:
  1. Red Light: Write a test that fails because the code does not exist yet.
  2. Green Light: Write the code to make the test pass.
  3. Refactor: Clean up the code while ensuring the test still passes.
• Advantages:
  1. Tests run automatically with every code check-in.
  2. Tests return clear results (true/false).
  3. Encourages developers to focus on the code they are about to write.
  4. Ensures that every piece of code has a corresponding test.
  5. Provides quick feedback and increases confidence in the code.
  6. Facilitates continuous integration.

Five Stages of Testing

1. Development Testing:

   • Includes unit testing (TDD), component testing, and system testing.
   • Focuses on finding bugs and defects.

2. Component Testing:

   • Tests interactions between related groups of objects.

3. System Testing:

   • Tests the entire system as a whole.
   • Focuses on component interactions and finding defects like crashes or incorrect computations.

4. Release Testing:

   • Conducted by a separate team to validate that the system meets stakeholder requirements.
   • Types:
     • Alpha Testing: Early testing by a small group of users.
     • Beta Testing: Wider testing by a larger group of users.
     • Acceptance Testing: Final testing by customers to decide if the software is ready for deployment.

5. User Testing:

   • Performed by end-users in their own environment.

Testing Techniques

Partition Testing

• Identify groups of inputs with common characteristics.
• Focus on edge cases (e.g., maximum and minimum values).

Example:

assertTrue(add(1, 2) == 3);
assertTrue(add(Integer.MAX_VALUE, -1) == Integer.MAX_VALUE - 1);
assertTrue(add(Integer.MAX_VALUE, 1) == Integer.MIN_VALUE); // Overflow test

Guideline-Based Testing

• Use experience to identify common errors.
• Examples:
  • Overwhelming the system (e.g., ordering 10,000 items).
  • Passing null values to methods.

Black-Box vs. White-Box Testing

• Black-Box Testing: Test without knowledge of the internal code.
• White-Box Testing: Test with full knowledge of the internal code.

Testable Software

1. Methods Should Return a Value:

   • Avoid void methods as they are harder to test.

2. Predictable Results:

   • Avoid randomness in methods.

3. Environment Independence:

   • Software should not rely on specific hardware or environments.
   • Example: Self-driving car software can be tested without a physical car.

Continuous Integration and Pipelines

• Definition: Automate the process of integrating code changes and running tests.
• Goal: Minimize lag time between code check-in and feedback.

---