Non-functional testing is the process of testing the non-functional aspects of a system, including its performance, security, accessibility, or usability.
Its counterpart is functional testing. Functional testing checks the system's features, while non-functional testing checks how well it operates.
Non-functional Testing vs Functional Testing
Here's a simple table to compare the differences between functional testing vs non-functional testing:
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Aspect
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Functional Testing
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Non-Functional Testing
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Focus
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What the software does (features, user interactions).
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How the software behaves under various conditions.
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Testing Criteria
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UI, API, user journeys, system interactions.
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Performance, security, scalability, usability, etc.
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Example
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Checking if a login button works.
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Checking if the login process takes <2 seconds under load.
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Read More: What is Functional Testing? A Complete Guide
Types of Non-Functional Testing
- Performance Testing - Measures how well a system performs under various conditions, including speed, responsiveness, and stability.
- Load Testing - Simulates multiple users accessing the system simultaneously to measure response time and resource consumption under expected traffic.
- Stress Testing - Pushes the system beyond its operational limits to see how it handles extreme conditions, such as high traffic spikes or limited resources.
- Scalability Testing - Assesses how well the system can scale up (handle more users) or scale down (reduce resources) without performance degradation.
- Volume Testing - Evaluates how the system handles massive amounts of data, such as database transactions, large file uploads, or extensive logging.
- Security Testing - Examines the software for vulnerabilities that could be exploited by hackers or unauthorized users.
- Penetration Testing - Simulates real-world cyberattacks to identify weaknesses in the system's security defenses.
- Authentication Testing - Verifies that login mechanisms, multi-factor authentication (MFA), and access permissions function correctly.
- Data Encryption Testing - Ensures that sensitive data is properly encrypted both in transit (during communication) and at rest (when stored).
- Usability Testing - Determines how intuitive and user-friendly the software is by analyzing user interactions and feedback.
- Accessibility Testing - Checks if the software is usable by individuals with disabilities, ensuring compliance with WCAG (Web Content Accessibility Guidelines).
- Readability Testing - Assesses whether text content is clear, concise, and understandable by the target audience, considering font size, contrast, and layout.
- Compatibility Testing - Ensures the software runs smoothly across different platforms, including multiple browsers (Chrome, Firefox, Edge), operating systems (Windows, macOS, Linux), and devices (desktop, mobile, tablet).
Benefits of Non-functional Testing
- Improves user satisfaction and system performance.
- Reduces downtime and operational risks.
- Helps businesses meet compliance and security standards.
- Ensures scalability for future growth.
Challenges of Non-functional Testing
- Complex setup - Requires specialized tools, environments, and configurations.
- Resource-intensive - Demands high computational power and skilled testers.
- Difficult to measure - Performance, usability, and security can be subjective.
- Time-consuming - Requires extensive testing under different conditions.
- Integration issues - Ensuring non-functional tests work across diverse systems.
- Constant updates - Changing security threats and performance benchmarks.
Non-functional Testing Key Metrics
- Response Time - Time taken to process a request.
- Throughput - Number of transactions per second.
- CPU & Memory Usage - System resource consumption under load.
- Error Rate - Frequency of failures or crashes.
- Scalability - System's ability to handle increasing loads.
- Uptime/Downtime - System availability percentage.
- Security Vulnerabilities - Number and severity of security risks.
- User Satisfaction Score - Feedback from usability tests.
- Compliance Score - Adherence to industry standards and regulations.
How To Perform Non-functional Testing?
1. Define Testing Requirements - Identify key performance indicators (KPIs) such as response time, server uptime, maximum concurrent users, and security standards. Define system constraints, including hardware limitations, bandwidth, and compliance requirements.
2. Select the Right Tools - Choose appropriate tools based on the type of non-functional testing required:
- Performance Testing - JMeter, LoadRunner, Gatling (for testing load, stress, and scalability).
- Security Testing - OWASP ZAP, Burp Suite (for penetration testing, authentication security, and encryption verification).
- Usability Testing - Hotjar, Crazy Egg (for analyzing user behavior, navigation flow, and accessibility).
3. Set Up Test Scenarios - Design test cases that mimic real-world conditions:
- For load testing, define concurrent users and expected transaction rates.
- For stress testing, set extreme conditions like high CPU/memory usage.
- For security testing, simulate attack scenarios such as SQL injection and cross-site scripting (XSS).
- For usability testing, include scenarios involving different user demographics and devices.
4. Execute Tests & Analyze Results -
- Run tests in various environments, such as staging, production-like, or cloud-based test setups.
- Monitor system behavior using logs, analytics, and performance reports.
- Identify and document bottlenecks, security vulnerabilities, and user experience issues.
- Provide recommendations for optimization, such as improving response times, increasing security layers, or enhancing UI intuitiveness.
Read More: Test Execution: A Detailed Guide
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