Software Testing and Maintenance Essentials

Software Validation and Verification Fundamentals

Objectives of Validation and Verification

• Detect and correct defects as soon as possible.
• Reduce risks of budget and timetable deviations.
• Improve software quality and reliability.
• Improve development process management visibility.
• Quickly assess proposed changes.

Philosophy of Software Testing

Recommendations by G.J. Myers:

• Each test case should define the expected output.
• Programmers must avoid testing their own programs.
• Thoroughly inspect test results to identify possible symptoms of defects.
• Test case generation should include valid, invalid, and unexpected inputs.
• Prove that the software performs as intended and avoids unintended actions.
• Test plans should always assume the presence of defects to avoid wasting resources.
• Testing is as creative, or more creative, than software development.

Software Testing Approaches

Black Box vs. White Box Testing

• Black Box approach: Studies functions and tests all possible program inputs and outputs.
• White Box testing: Focuses on the program's internal structure to select test cases, aiming to test all possible execution paths and identify potential breakage points.

White Box Structural Testing Criteria

• Statement Coverage: Each statement is executed at least once.
• Decision Coverage: Every decision must yield both true and false results.
• Condition Coverage: Every condition within a decision takes both true and false values at least once.
• Decision/Condition Coverage: Combines condition coverage with decision coverage.
• Multiple Condition Coverage.

Software Development Lifecycle Phases

The V-Model Testing Phases

• Unit Testing: Focuses on the module's logic and its functions.
• Integration Testing: Considers module grouping mechanisms within the program structure.
• System Testing: Focuses on meeting overall system objectives.
• Acceptance Testing: Allows the user to verify the final product.

Software Audit Principles

Objective: Objectively confirm that products and/or development processes meet project standards, specifications, and procedures. Typically performed by external personnel.

Product Walkthroughs

Objective: Evaluate a product for defects, improve compliance with standards, and consider solutions to identified problems.

Software Maintenance and Review

Types of Software Maintenance

The process of modifying a software system or component post-delivery to correct faults, improve performance or other attributes, or adapt to a changing environment.

• Perfective Maintenance (60%): Improves or adds new functionality as required by the user.
• Adaptive Maintenance (18%): Adapts the system to changes in its technological environment.
• Corrective Maintenance (17%): Corrects hardware or software defects detected by users.
• Preventive Maintenance (5%): Aims to prevent future system issues.

Software Product Revision

Consists of a meeting where a group of people review a product to identify any issues.