Software testing is one of the most important phases in the software development life cycle (SDLC). Whether you are preparing for your first interview or aiming to strengthen your fundamentals, having a strong understanding of testing concepts is crucial.
This article covers 40 of the most commonly asked software testing interview questions, with clear explanations and real-world examples.
Let’s begin!
1. What is the PDCA Cycle and where does software testing fit?
The PDCA (Plan–Do–Check–Act) cycle is a continuous improvement process used in software development:
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Plan: Define goals, requirements, and strategies.
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Do: Build the product according to the plan.
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Check: Evaluate the product through testing.
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Act: Fix issues and improve the product.
Testing belongs to the “Check” phase, where testers ensure the software meets expectations and requirements.
2. Difference between White Box, Black Box, and Gray Box Testing
Black Box Testing
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Depends only on requirements and specifications
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Tester doesn't know internal code
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Example: Functional testing, system testing
White Box Testing
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Depends on internal structure, logic, code paths
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Generally done by developers
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Example: Code review, unit testing
Gray Box Testing
3. What is Usability Testing?
Usability testing checks how easy and user-friendly a software application is.
Here, real customers (or sample users) interact with the prototype or application.
Focus areas include:
Best performed using mockups/prototypes in early stages of development.
4. Categories of Defects
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Wrong: Functionality implemented incorrectly.
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Missing: A required feature was not implemented.
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Extra: A feature not asked by the customer was added.
Even an extra feature is considered a defect because it deviates from requirements.
5. How to define a Testing Policy in an organization?
A testing policy helps unify testing practices across projects. Key steps:
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Definition: Create a common definition of testing.
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How to Achieve: Define processes, committees, test plans, and guidelines.
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Evaluation: Use metrics to measure effectiveness (defects/KLOC, efficiency).
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Standards: Set benchmarks for acceptable quality levels.
6. Basis of Preparing an Acceptance Test Plan
Acceptance testing is prepared using:
These documents help testers understand what the user expects from the system.
7. What is Configuration Management?
Configuration management involves recording and tracking changes to various artifacts:
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Source code
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Test cases
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Requirement documents
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Design documents
It ensures version control, reduces chaos, and enables rollback when needed.
8. How Does a Coverage Tool Work?
A coverage tool runs alongside testing and tracks:
This helps identify missing test areas.
9. Which is the Best Testing Model?
There is no universal “best” model, but:
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Tailored models (combined features of Waterfall, Iterative, Agile) fit most organizations.
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For pure testing projects, the V-Model is most effective.
10. Defect vs. Failure
11. Should Testing Begin Only After Development?
No. Testing should happen in every phase of SDLC:
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Requirements — verification
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Design — review
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Coding — unit testing
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Testing — functional/system tests
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Maintenance — regression testing
Early testing reduces cost significantly.
12. Where do more defects occur — Design or Coding phase?
Around 60% of defects occur in the design phase and 40% during execution.
Design flaws cause architectural issues that affect development later.
13. Which Teams Can Perform Testing?
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Dedicated test team
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Outsourced testers
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In-house QA/QC
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Developers
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End users (UAT)
14. Types of Defect Impact Ratings
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Minor: Small issues, do not affect main operations
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Major: Impacts large portions of functionality
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Critical: Stops system function completely
15. Does More Testing Always Improve Quality?
No. Only 20% of test cases are high-value.
Over-testing increases cost without major benefits.
Under-testing increases defect leakage.
A balance is required.
16. Relationship Between Environment Reality & Test Phases
Realistic environments become more important as testing progresses:
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Unit testing → partially real environment
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System testing → more real
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Acceptance testing → 100% real customer environment
17. Types of Verifications (Static Testing)
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Walkthrough: Informal checking done by the author with peers
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Inspection: Formal, structured review of documents/code
18. Test Documents Across the SDLC
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Central Test Plan — prepared before the project starts
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Acceptance Test Plan — prepared with customer
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System Test Plan — starts during design
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Integration & Unit Test Plans — start during development
19. Which Test Cases Are Written First?
Black box test cases are created first because requirement documents are available early.
White box test cases require architecture details and are written later.
20. Explain Different Testing Levels
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Unit Testing: Individual modules
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Integration Testing: Multiple modules combined
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System Testing: Entire system as a whole
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Acceptance Testing: Customer validates business needs
21. What is a Test Log?
A test log is a chronological record of test execution details including:
22. What is Requirement Traceability?
Traceability ensures every requirement is mapped to:
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Test cases
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Design documents
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Development tasks
It confirms complete test coverage.
23. What Are Entry and Exit Criteria?
Entry criteria → Conditions required to begin testing
Exit criteria → Conditions required to end testing
Example:
Exit criteria may include “no critical defects open”.
24. Verification vs Validation
25. Latent vs Masked Defects
26. What is Calibration?
Checking and maintaining the accuracy of devices/tools used for testing and production.
27. Alpha vs Beta Testing
28. How Does Testing Reduce Risk?
Testing cannot eliminate risk but reduces it by detecting defects early, minimizing failures in production.
29. Types of Test Coverage Techniques
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Statement coverage — every line executed
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Decision coverage — all true/false conditions
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Path coverage — every logical path tested
30. Cost Impact of Late Defect Removal
Fixing defects in later phases is 20x more costly than fixing in requirement/design phase.
Late defects require rework, regression testing, and documentation updates.
31. User Inputs Needed for Proper Testing
32. What is the Workbench Concept?
A workbench defines how a task is performed:
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Input
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Execute
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Check
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Output
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Rework (if needed)
Used to formalize testing activities.
33. What is Defect Cascading?
A single defect triggering multiple defects in later stages is defect cascading.
Example: Wrong tax calculation affecting ledger and reports.
34. What is Cohabiting Software?
Multiple applications sharing system resources can affect each other.
After installing your app, other owners should test theirs too.
35. Pilot vs Beta Testing
36. Different Rollout Strategies
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Pilot
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Gradual Implementation
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Phased Implementation
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Parallel Implementation
Each has pros and cons based on complexity and cost.
37. System Testing vs Acceptance Testing
38. Regression Testing vs Confirmation Testing
39. What is the Importance of a Real Test Environment?
A testing environment must match production to prevent unexpected issues during deployment.
40. Why Should Testers Be Involved in Requirements Phase?
Early involvement helps:
Conclusion
Software testing is not just about finding defects—it's about ensuring quality, reliability, and customer satisfaction. Understanding the concepts in this guide will help you confidently face interviews and also improve your practical knowledge as a tester.
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