Functional Testing And Nonfunctional Testing: Key Differences

What is Functional Testing?

• Definition: A type of black-box testing that validates a software system's behavior against defined functional requirements. It verifies that the system produces the correct outputs in response to specific inputs, without concern for the underlying code implementation.

Focus:

• Behavior: What the system does
• .Requirements: Alignment with documented specifications
• .Inputs and Outputs: Verifying the accuracy of results based on input data.
• Purpose: To ensure the system meets the user's needs and expectations as outlined in the functional requirements.

Types of Functional Tests:

• Unit Tests: Test individual units or components of code in isolation.
• Integration Tests: Test how different units or modules of the system work together.
• System Tests: Test the entire system as a whole under real-world conditions.
• Smoke Tests: A basic suite of tests to quickly check core functionality after a new build is deployed.
• Regression Tests: Ensure that existing, previously working functionality remains correct after code changes or updates.

Example: Online Payment Form

Functional Requirements:

• Accepts valid credit card numbers (16 digits)
• Accepts valid expiration dates (MM/YY format)
• Accepts valid CVV codes (3 digits or 4 for Amex)
• Calculates correct total amount based on item prices and tax.
• Displays an error message if any of the above validations fail.
• Upon successful validation, submits the payment securely to the processor.

Functional Test Cases:

• Positive tests: Enter valid credit card, expiration, CVV, and purchase amount -> Expect successful payment confirmation.
• Negative tests: Enter less than 16 digits for credit card -> Expect "Invalid Card Number" error.Enter past expiration date -> Expect "Card Expired" error.Omit CVV -> Expect "CVV Required" error.
• Boundary Tests: Enter a 16-digit credit card at the upper limit and below the lower limit of valid card numbers.

Key Points:

• Functional testing is based on "what" the system does, not "how" it does it (implementation is not the focus).
• Test cases are derived directly from the detailed functional requirements document.

What is Non-functional Testing?

• Definition: A type of testing that focuses on the operational qualities of a software system, rather than its specific behaviors. It assesses how well the system performs under various conditions, along with aspects like usability, security, and compatibility.
• Focus:Performance: How fast the system responds, its capacity, and how it handles load.
• Usability: How easy and intuitive the system is for users to navigate and use.Reliability: How consistently the system functions correctly over time.
• Security: How well the system protects data and resists vulnerabilities.Compatibility: How well the system functions across different browsers, devices, and operating systems.
• Purpose: To ensure the system meets implicit or explicit expectations regarding its quality characteristics, not just its core functions.

Types of Non-Functional Tests:

• Performance testing: Measures response time, throughput, and resource usage under various loads.
• Load testing: Evaluates how the system behaves under heavy user demand.
• Stress testing: Pushes the system beyond its limits to identify breaking points and recovery mechanisms.
• Usability testing: Assesses user experience with tasks, navigation, and overall ease of use.
• Security testing: Identifies vulnerabilities, potential attack vectors, and data protection measures.
• Compatibility testing: Checks performance and functionality across different environments.

Example: E-commerce Website

Non-Functional Requirements:

• Page load time under 2 seconds, even during peak traffic.
• Ability to handle 1,000 concurrent users without significant slowdown.
• Uptime of 99.99%.
• The user interface is intuitive enough for first-time visitors to easily find products and complete purchases.
• Secure storage of customer credit card information and adherence to PCI compliance.
• Seamless display and functionality across popular web browsers and mobile devices.

Non-Functional Test Cases:

• Performance test: Simulate 500 users simultaneously browsing and measure average page load times.
• Load test: Gradually increase simulated users to 1,500 and monitor system responsiveness.
• Security test: Conduct penetration testing to attempt various exploit techniques.
• Usability test: Conduct user sessions with real participants and observe their ability to complete common tasks.
• Compatibility test: Run the website on Chrome, Firefox, Safari, and Edge on both desktop and major mobile devices.

Key Points:

• Non-functional testing verifies "how well" the system works, not just the "what".
• Non-functional requirements are often as crucial as functional ones for customer satisfaction.
• Measurement and metrics are key to quantifying non-functional test results (e.g., load time in seconds, number of successful vs. failed transactions during stress, etc.).