Static vs Dynamic Testing: Complete Guide for ISTQB CTFL Exam

Static vs Dynamic Testing: Complete Guide for ISTQB CTFL Exam

Why This Topic Is Important

Understanding the differences between static and dynamic testing is fundamental to the ISTQB CTFL certification. This concept forms the foundation of modern quality assurance practices and is heavily tested in the exam. Mastering these distinctions will help you:

• Identify which testing approach is most suitable for different scenarios
• Understand the cost-benefit analysis of each testing method
• Make informed decisions about test strategy and planning
• Answer multiple-choice questions with confidence
• Apply testing principles effectively in real-world projects

What Is Static vs Dynamic Testing?

Static Testing Definition

Static testing is a form of quality assurance that examines software work products without executing code. It involves reviewing, analyzing, and inspecting documents, code, and other artifacts to identify defects, inconsistencies, and areas for improvement before the software is run.

Dynamic Testing Definition

Dynamic testing is a form of quality assurance that evaluates software behavior by executing the code. It involves running the software with test cases and comparing actual results against expected results to identify defects and validate functionality.

Key Differences Between Static and Dynamic Testing

Static Testing Techniques

1. Informal Reviews

A casual examination where one or more team members discuss the work product without formal procedures.

2. Walkthroughs

The author leads the team through the work product, explaining it section by section. Focus is on gaining understanding.

3. Technical Reviews

Formal examination of a work product led by a peer to identify defects and ensure compliance with standards.

4. Inspections

The most formal type of review with defined roles (moderator, scribe, author, inspectors), checklists, and metrics. Highly structured process.

5. Static Analysis

Automated examination of code using tools to identify potential defects without executing the code (e.g., code analyzers, linters).

Dynamic Testing Techniques

1. Unit Testing

Testing individual components or functions in isolation, typically performed by developers.

2. Integration Testing

Testing the interaction between integrated modules or components.

3. System Testing

Testing the complete system against specified requirements.

4. Acceptance Testing

Testing to determine whether the system meets user requirements and is ready for delivery.

5. Performance Testing

Testing system performance characteristics like speed, scalability, and stability under load.

How Static Testing Works

The Static Testing Process:

1. Planning: Define the scope, objectives, and schedule for the review or inspection.
2. Overview: Team members familiarize themselves with the work product.
3. Preparation: Individual reviewers examine the work product independently and identify issues.
4. Review Meeting: The team meets to discuss findings in an organized manner.
5. Rework: The author addresses the identified issues and makes corrections.
6. Follow-up: Verify that all issues have been properly resolved.

How Dynamic Testing Works

The Dynamic Testing Process:

1. Test Planning: Define test objectives, scope, and strategy.
2. Test Design: Create test cases based on requirements and specifications.
3. Test Setup: Prepare the test environment and test data.
4. Test Execution: Run the test cases and record actual results.
5. Comparison: Compare actual results with expected results.
6. Defect Logging: Document any discrepancies as defects.
7. Regression Testing: Re-test after fixes to ensure no new issues are introduced.

Advantages and Disadvantages

Static Testing Advantages:

• Finds defects early in the development lifecycle
• Reduces cost of fixing defects (cheaper to fix early)
• Improves code quality and standards compliance
• Provides immediate feedback to the development team
• Can identify issues before code compilation
• Supports knowledge transfer and team learning
• Catches logical errors and design flaws

Static Testing Disadvantages:

• Cannot find runtime or environment-specific defects
• Requires trained and experienced reviewers
• Time-consuming for large work products
• Success depends heavily on reviewer expertise
• May miss defects that only appear during execution

Dynamic Testing Advantages:

• Finds runtime defects and integration issues
• Validates actual system behavior
• Tests performance and resource usage
• Can be automated for efficiency
• Provides evidence of system functionality
• Identifies defects in edge cases and unusual scenarios
• Confirms that fixes actually work

Dynamic Testing Disadvantages:

• Defects are found late in development (more expensive to fix)
• Cannot test all possible scenarios
• Requires complete or near-complete code
• More time and resources needed
• Test coverage may be limited
• Cannot detect some code quality issues

Relationship Between Static and Dynamic Testing

Static and dynamic testing are complementary, not mutually exclusive. A comprehensive testing strategy should include both approaches:

• Static testing catches defects early and is cost-effective
• Dynamic testing validates actual runtime behavior
• Together, they provide comprehensive quality assurance
• Using both approaches significantly reduces the number of defects that reach production

Common ISTQB Exam Questions and How to Answer Them

Question Type 1: Identification of Static vs Dynamic Testing

Example: "Which of the following is an example of dynamic testing?"

How to Answer:

• Look for keywords: executing, running, test cases, results
• Dynamic testing ALWAYS involves running the code
• If the answer mentions reviewing, checking, or inspecting without execution, it's static testing
• Examples of dynamic testing: unit testing, integration testing, system testing, functional testing

Question Type 2: Sequencing and Timing

Example: "At which phase of the software development lifecycle is static testing most effective?"

How to Answer:

• Remember: Static testing happens EARLY in the SDLC
• It can start as soon as documents or code exist
• Static testing can be performed on requirements, design documents, and code before compilation
• Dynamic testing comes LATER when the software is executable

Question Type 3: Cost and Defect Analysis

Example: "Why is it more cost-effective to find defects through static testing rather than dynamic testing?"

How to Answer:

• Static testing finds defects early
• Early defects are cheaper to fix
• Late defects (found in dynamic testing) require more rework
• The cost of fixing a defect increases the later it's discovered
• Prevention is cheaper than correction

Question Type 4: Applicable Techniques

Example: "Which of the following is a static testing technique?"

How to Answer:

• Static techniques: Reviews, walkthroughs, inspections, technical reviews, static analysis
• Dynamic techniques: Testing, unit testing, integration testing, system testing
• If you see "review" or "inspection" in the answer, it's likely static testing

Question Type 5: Defect Types

Example: "Static testing is particularly effective at finding which type of defect?"

How to Answer:

• Static testing finds: design flaws, logical errors, syntax errors, standards violations, missing requirements
• Dynamic testing finds: runtime errors, performance issues, integration problems, functional defects

Exam Tips: Answering Questions on Differences Between Static and Dynamic Testing

Tip 1: Focus on Code Execution

The fundamental distinction is whether code is executed or not. If the question mentions running, executing, or performing actions with test cases, it's dynamic testing. If it's about reviewing or analyzing without execution, it's static testing.

Tip 2: Remember the Timeline

Create a mental timeline: Static testing occurs FIRST (during requirements, design, and coding phases). Dynamic testing occurs LATER (during testing phases). This helps you answer timing-related questions correctly.

Tip 3: Think About Cost-Effectiveness

When a question asks about cost-effectiveness or early defect detection, the answer is usually static testing. When it asks about validating actual behavior or finding runtime issues, it's dynamic testing.

Tip 4: Recognize Technique Names

Memorize these:

• Static: Review, walkthrough, inspection, technical review, static analysis
• Dynamic: Unit test, integration test, system test, acceptance test, functional test, performance test

Tip 5: Use Process of Elimination

If an answer choice mentions a testing tool that executes code (like Selenium, JUnit, LoadRunner), it's dynamic testing. If it mentions review tools or static analyzers (like SonarQube, Checkstyle), it's static testing.

Tip 6: Watch for "Both" or "Complementary" Answers

Many exam questions test whether you understand that static and dynamic testing are complementary. If an answer suggests using both approaches together, it's often correct.

Tip 7: Understand the Defect Cost Curve

A key concept: The cost of fixing a defect increases exponentially through the development lifecycle. This is why static testing (early detection) is emphasized in ISTQB. When questions discuss cost, remember this principle.

Tip 8: Read Keywords Carefully

Watch for subtle words:

• "Without executing code" = Static testing
• "By executing code" = Dynamic testing
• "Early phase" = Typically static testing
• "Actual behavior" = Dynamic testing

Tip 9: Practice with Past Questions

ISTQB frequently asks questions comparing these two approaches. Practice with sample questions to recognize common patterns and trap answers.

Tip 10: Consider the Context

Always consider the scenario presented in the question:

• If it's about reviewing a design document before coding = Static testing
• If it's about running the application and checking outputs = Dynamic testing
• If it's about measuring code quality metrics = Could be either, but likely static if automated analysis

Tip 11: Know the Goals

Static Testing Goals:

• Find defects early
• Improve code quality
• Ensure standards compliance
• Support knowledge transfer

Dynamic Testing Goals:

• Validate functionality
• Find runtime defects
• Verify non-functional requirements
• Confirm system behavior

Tip 12: Study the V-Model

Understanding the V-model helps you see when each type of testing is applied:

• Left side (development): Static testing of requirements, design, and code
• Right side (testing): Dynamic testing at various levels (unit, integration, system, UAT)

Practice Exam Questions

Question 1:

What is the main difference between static and dynamic testing?

A) Static testing is less expensive than dynamic testing
B) Static testing does not involve code execution while dynamic testing does
C) Static testing only finds syntax errors
D) Dynamic testing cannot be automated

Answer: B
Explanation: While A is partially true, B is the defining characteristic. Static testing by definition does not execute code, while dynamic testing requires code execution.

Question 2:

Which of the following is an example of static testing?

A) Functional testing
B) Performance testing
C) Code inspection
D) System testing

Answer: C
Explanation: Code inspection is a static testing technique (a formal review). The other options all involve executing code (dynamic testing).

Question 3:

At what stage of the software development process should static testing ideally be performed?

A) Only after the software is fully coded
B) Early, starting from requirements and design phase
C) Only during the test phase
D) Static testing should not be performed before dynamic testing

Answer: B
Explanation: Static testing is most cost-effective when performed early. It can start as soon as requirements or design documents exist, before or during coding.

Question 4:

Which statement about static testing is correct?

A) Static testing finds all runtime errors
B) Static testing finds defects before code execution
C) Static testing requires a fully compiled program
D) Static testing is more expensive than dynamic testing

Answer: B
Explanation: Static testing by definition finds defects before code execution. Options A and C are incorrect because static testing doesn't require execution. Option D is false because static testing is generally cheaper.

Question 5:

A development team wants to ensure high code quality and reduce the cost of defect fixing. Which approach should they prioritize?

A) Only dynamic testing after development is complete
B) Both static and dynamic testing throughout the development lifecycle
C) Only static testing before dynamic testing
D) Dynamic testing before any static testing

Answer: B
Explanation: While static testing finds defects early, dynamic testing validates actual behavior. A comprehensive strategy uses both approaches. Option B reflects the modern quality assurance best practice of complementary testing approaches.

Summary Checklist for Exam Preparation

Before the exam, ensure you can:

• Define static and dynamic testing clearly
• List at least 3 static testing techniques (reviews, inspections, static analysis, walkthroughs)
• List at least 3 dynamic testing techniques (unit, integration, system testing)
• Explain the cost-benefit relationship between early defect detection and fixing costs
• Identify when each approach should be used in the SDLC
• Recognize keywords that indicate static vs dynamic testing
• Understand that these approaches are complementary
• Explain why certain defects are better caught by static or dynamic testing
• Answer scenario-based questions confidently
• Solve practice questions without referring to notes

Final Thoughts

The distinction between static and dynamic testing is crucial for ISTQB CTFL success. Remember that these are not competing approaches but complementary strategies that together provide comprehensive quality assurance. The exam will test your understanding through various question types, so practice identifying these approaches in different contexts. Focus on the fundamental difference (code execution vs. no execution), understand the timeline (static is early, dynamic is later), and remember the cost implications. With consistent practice and clear understanding, you'll answer these questions confidently on exam day.