QA Fundamentals Interview Questions and Answers
Testing principles, test levels and types, test design techniques (equivalence classes, boundary values, decision tables, pairwise), bug reports and severity, test plans and strategy, exploratory and risk-based testing, API, performance and security checks, and QA in Agile teams.
226 questions for QA Fundamentals interviews with answers and explanations - Junior, Middle and Senior levels. Sample questions, online quizzes and coding tasks.
- Test design
- Bug reports
- Test levels
- Risk-based testing
- ISTQB
Questions by level
Junior
Core concepts and syntax · 50 questions
Middle
Practice, nuances and optimization · 50 questions
Senior
Architecture, internals, edge cases · 50 questions
Sample questions
A few questions from each level with the correct answer and an explanation.
QA Fundamentals · Junior
- What is the main purpose of software testing?
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Correct answer: To find defects and give information about quality and risk
Testing reduces risk by finding problems and showing how the product behaves, so people can decide whether to release. It can show that defects exist, but it can never prove that there are none.
- How do QA, QC and testing relate to each other?
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Correct answer: QA improves the process, QC checks the product, testing is part of QC
Quality assurance is about preventing defects through good processes (reviews, standards, definitions of done). Quality control checks the product itself, and testing is the main QC activity.
- What is the difference between an error, a defect and a failure?
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Correct answer: A person makes an error, it causes a defect in code, which can cause a failure
A developer's mistake (error) leaves a defect (bug, fault) in the code or documentation. When that code runs under certain conditions, the system behaves wrongly: that is a failure. Not every defect leads to a failure.
- Which statement matches the testing principle 'exhaustive testing is impossible'?
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Correct answer: You can't test every input and path, so you prioritize by risk
Even a simple form with a few fields has more input combinations than anyone could run. Instead, testers use techniques and risk analysis to choose the tests that matter most.
QA Fundamentals · Middle
- When is decision table testing most useful?
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Correct answer: When the result depends on combinations of several conditions
A discount that depends on 'is member', 'order over 100' and 'has coupon' has 8 combinations. A decision table lists them all, so none is missed, and shows which can be merged.
- A rule has 3 independent yes/no conditions. How many columns does a full decision table have?
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Correct answer: 8
Each condition doubles the combinations: 2 × 2 × 2 = 8. Impossible or equivalent combinations can then be collapsed to reduce the number of tests.
- When is state transition testing a good choice?
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Correct answer: When behaviour depends on the current state, like an order's status
An order goes New → Paid → Shipped → Delivered, and some transitions must be impossible (Shipped → New). A state diagram shows valid and invalid transitions to test.
- In state transition testing, why test invalid transitions?
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Correct answer: The system must reject them, e.g. refunding an unpaid order
Bugs often allow actions in the wrong state: cancelling a delivered order, paying twice. Tests should check that such transitions are refused with a clear message.
QA Fundamentals · Senior
- What should an organization-level test strategy define?
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Correct answer: Quality goals, test levels and types, tooling and how risk drives effort
A strategy gives consistent principles across teams (what to automate, which environments, how to report), while each project's plan adapts them to its own scope and risks.
- A team ships daily, but releases still fail in production. What is usually the most effective first move?
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Correct answer: Analyse escaped defects to find which test levels missed them
Escaped defect analysis shows the real gap: missing contract tests, untested configs, no monitoring. Adding slow gates everywhere hurts flow without targeting the cause.
- How do you measure the effectiveness of a QA process without rewarding the wrong behaviour?
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Correct answer: Track escaped defects, impact and lead time rather than bug counts
Bug counts and test case counts are easy to game and pit testers against developers. Outcome metrics (production incidents, time to detect, customer impact) reflect quality.
- Which DORA metric relates most directly to release quality?
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Correct answer: Change failure rate
Change failure rate is the share of deployments causing a failure in production. With time to restore service, it balances speed metrics like deployment frequency.
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