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ISTQB Telephonic Interview Questions & Answers

30 questions for the telephonic interview stage — 17 easy, 12 medium, 1 hard.

About the telephonic interview round

The telephonic or screening round is a 15-30 minute call with a recruiter or engineer. It checks your basics, your CV and whether you can explain ISTQB concepts clearly without a screen to point at.

Tips for the telephonic interview round

  • Keep your CV in front of you and be ready to explain every line on it.
  • Answer in short, clear sentences; there is no whiteboard, so structure matters.
  • Take the call somewhere quiet and confirm the time in advance.
  • Prepare one question to ask the interviewer at the end.
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01

What are the risks of test automation?

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Unrealistic expectations about what a tool can do; inaccurate estimates of the time, cost and effort to introduce and maintain it; using a tool where manual testing is better; relying on the tool too much and ignoring critical thinking; dependency on the tool vendor, which may go out of business or retire the tool; open-source tools being abandoned; and tools not compatible with the development platform or not meeting regulations.
02

Which good testing practices apply regardless of the SDLC model?

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CTFL v4.0 lists these: for every software development activity there is a corresponding test activity; each test level has its own specific objectives; test analysis and design for a level begin during the corresponding development phase; and testers are involved in reviewing work products as soon as drafts are available. Together these practices support early testing and quality control in waterfall, V-model and Agile projects alike.
03

Explain the four test types defined in CTFL v4.0.

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Functional testing checks what the system should do, covering completeness, correctness and appropriateness. Non-functional testing checks how well it behaves, using ISO/IEC 25010 characteristics such as performance efficiency, usability, security, reliability, compatibility, maintainability and portability. Black-box testing is specification-based, and white-box testing is structure-based. Any test type can be applied at any test level, with a different focus at each.
04

What is the value of static testing?

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Static testing detects defects in the earliest phases, when they are cheapest to fix. It finds defects that dynamic testing cannot, such as unreachable code or defects in non-executable work products. It helps evaluate quality and build confidence, improves shared understanding among stakeholders, and gives fast feedback on code through static analysis in CI. Reviews cost effort, but the total cost of quality is usually lower.
05

How does testing relate to quality assurance and quality control?

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Testing is a form of quality control (QC): a product-oriented, corrective approach that checks work products. Quality assurance (QA) is process-oriented and preventive: it improves processes on the idea that a good process produces a good product. Test results are used by both. QC uses them to fix defects, and QA uses them as feedback on how well the development and test processes are performing.
06

What does 'defects cluster together' mean and how is it used?

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A small number of components usually contain most of the defects or cause most operational failures, similar to the Pareto principle. Predicted and observed defect clusters are an important input to risk-based testing, so testers focus more effort on those areas. Example: in a banking app, the interest calculation and payment modules may hold most reported defects, so they get deeper and more frequent regression coverage.
07

What does a test plan contain according to CTFL v4.0?

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A test plan typically covers: context of testing (scope, objectives, constraints, test basis); assumptions and constraints; stakeholders with roles and responsibilities; communication; a risk register of product and project risks; the test approach (test levels, types, techniques, deliverables, entry and exit criteria, independence, metrics, test data and environments); and budget and schedule. It documents how test objectives will be met and is updated as the project changes.
08

What is static testing and how is it different from dynamic testing?

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Static testing examines work products without executing them, through manual reviews or static analysis tools. Dynamic testing executes the software. Static testing finds defects directly, such as ambiguous requirements or coding standard violations, while dynamic testing causes failures whose defects are then located by debugging. Static testing works on non-executable products like requirements and test plans, and finds defects dynamic testing cannot, such as unreachable code.
09

A field accepts integers from 1 to 99. Which set of values achieves 100 percent 2-value BVA coverage: {1, 99}, {0, 1, 99, 100}, {0, 50, 100} or {1, 2, 98, 99}?

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The answer is {0, 1, 99, 100}. Two-value BVA needs each boundary value and its closest neighbour in the adjacent partition: 0 and 1 at the lower edge, 99 and 100 at the upper edge. {1, 99} misses the invalid neighbours, {0, 50, 100} misses 1 and 99, and {1, 2, 98, 99} stays inside the valid partition, which is closer to 3-value thinking.
10

What are the benefits of test automation?

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Automation saves time by reducing repetitive manual work such as regression runs, comparisons and data entry. It prevents simple human errors through greater consistency and repeatability. It gives more objective assessment, such as coverage, and access to measurements too complex for humans. It reduces test execution times, giving faster feedback and earlier defect detection, and frees testers to design new and deeper tests.
11

How does the choice of SDLC model affect testing?

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In sequential models like waterfall and the V-model, testers join early for reviews and planning, but dynamic testing happens later once code exists. In iterative and incremental models such as Scrum, every iteration delivers a working increment, so static and dynamic testing happen at all levels in each iteration, regression testing is critical and automation is usually needed. The model affects scope, timing, documentation, techniques and automation.
12

What are the objectives of a defect report?

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A defect report gives the people responsible for handling and resolving the defect enough information to fix it. It also provides a way to track the quality of the work product, and it offers ideas for improving the development and test processes. A good report is clear, reproducible and neutral in tone, so that developers can act on it quickly and managers can analyse trends.
13

What happens in test monitoring, test control and test completion?

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Test monitoring gathers information about testing to check progress and whether exit criteria are met, using metrics like test case progress, defect counts, coverage and cost. Test control uses that information to give guidance and corrective actions, such as reprioritising tests or changing the schedule. Test completion collects data from finished activities to consolidate experience, testware and other information, usually at milestones like release or end of iteration.
14

Tell me about a time you missed a defect. What did you learn?

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Situation: a defect in date formatting reached production after my testing. Task: understand why and prevent it. Action: I owned the miss, found my test data used only one locale, and added test cases for other date formats and locales. I also shared a checklist for locale testing. Result: no similar defect appeared in later releases, and I learned to review my test data as carefully as my test steps.
15

What are the main forms of acceptance testing?

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User acceptance testing is done by intended users. Operational acceptance testing is done by operations staff and covers backup, restore, installation and disaster recovery. Contractual and regulatory acceptance testing checks contract criteria or legal rules. Alpha testing is done by potential users at the developer's site, and beta testing by users at their own locations. Acceptance testing mainly builds confidence and validates fitness, not defect finding.
16

Tell me about a time a review you did prevented a serious problem.

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Situation: reviewing a refund user story, I noticed it did not say how partial refunds work on discounted orders. Task: clarify it before development started. Action: I logged the gap, set up a 15-minute call with the product owner and developer, and we added three acceptance criteria with worked examples. Result: the feature shipped without the refund calculation errors that had hurt an earlier release.
17

What categories of test tools does CTFL v4.0 describe?

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Test management tools, static testing tools, test design and implementation tools, test execution and coverage tools, non-functional testing tools, DevOps tools such as CI/CD pipelines and build tools, collaboration tools, and tools supporting scalability and deployment standardisation such as virtual machines and containers. Any tool that assists testing counts, even a spreadsheet. Tools improve efficiency, quality and repeatability.
18

What are the roles in a formal review?

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The manager decides what is reviewed and provides resources. The author creates and fixes the work product. The moderator, or facilitator, ensures meetings run effectively, mediating and managing time. The scribe, or recorder, collects anomalies and records decisions. Reviewers perform the review and may be team members, experts or stakeholders. The review leader takes overall responsibility, deciding who is involved and organising the review. One person can hold several roles.
19

Name the main test activities in the ISTQB test process.

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The test process has seven activity groups: test planning, test monitoring and control, test analysis, test design, test implementation, test execution and test completion. They are often iterative or done in parallel rather than strictly sequential. How they are carried out depends on context, such as the SDLC, product risks, budget, time, team skills and regulations, so an Agile team performs them in small loops in every iteration.
20

How is configuration management handled in a DevOps environment?

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In DevOps, configuration management is largely automated within the CI/CD pipeline. Source code, test scripts, pipeline definitions and infrastructure as code are all in version control. Each build gets a unique version, artefacts are stored in a repository, and environments are created from versioned templates. This makes test results reproducible and lets teams trace exactly which code, tests and configuration produced a given result.
21

Testing found 80 defects and users found 20 more after release. What is the defect detection percentage?

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DDP = defects found in testing / (defects found in testing + defects found after release) x 100 = 80 / (80 + 20) x 100 = 80 / 100 x 100 = 80 percent So testing caught 80 percent of known defects. Tracking DDP across releases shows whether test effectiveness is improving.
22

Which black-box test techniques are covered in CTFL v4.0?

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CTFL v4.0 covers four black-box techniques: equivalence partitioning, boundary value analysis (2-value and 3-value), decision table testing and state transition testing. They derive tests from the specification without looking at the internal structure, so tests stay valid even when the implementation changes. Use case testing, which was in older syllabi, is no longer part of the v4.0 Foundation syllabus.
23

What is the difference between confirmation testing and regression testing?

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Confirmation testing checks that an original defect has been fixed, by re-running the failed tests or new tests that cover the change. Regression testing checks that a change, including a fix, has not caused adverse effects elsewhere, in the same component, connected components or the environment. Regression suites grow and run often, so they are strong candidates for automation, typically inside a CI pipeline.
24

Which test estimation techniques are described in CTFL v4.0?

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Estimation based on ratios uses historical figures, such as a development-to-test effort ratio. Extrapolation uses measurements from the current project, for example averaging the last three iterations. Wideband Delphi is an expert-based technique where experts estimate separately and iterate until consensus; Planning Poker is an Agile variant. Three-point estimation uses optimistic, most likely and pessimistic values to calculate a weighted estimate and its standard deviation.
25

What do the K-levels K1, K2 and K3 mean in the CTFL syllabus?

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K-levels describe the cognitive level of each learning objective. K1 is remember: recall a term or fact, such as listing test levels. K2 is understand: explain, compare, classify or give examples, such as distinguishing project and product risks. K3 is apply: use a procedure in a given situation, such as deriving boundary values or calculating a three-point estimate. Most exam questions are K2.
26

What is the difference between verification and validation?

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Verification checks whether the system meets its specified requirements: 'Are we building the product right?' Validation checks whether the system meets user and stakeholder needs in its operational environment: 'Are we building the right product?' Both are testing objectives. Example: verification confirms the eight-character password rule is implemented, while validation checks that real users can actually register easily on a mobile phone.
27

A review is led by the author, and its goals are to educate the team and reach consensus. Which review type is it?

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It is a walkthrough. Walkthroughs are led by the author, and their objectives include educating reviewers, building consensus, generating new ideas, motivating authors and detecting anomalies. Individual preparation is optional. If a trained moderator led it with technical experts to make technical decisions, it would be a technical review; if it followed a fully formal process with metrics, it would be an inspection.
28

What does the principle 'tests wear out' mean, and what was it called earlier?

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In v4.0 the old 'pesticide paradox' was renamed 'tests wear out'. If the same tests are repeated many times, they become less effective at finding new defects because the code they exercise has already been fixed. Testers should modify existing tests and test data and write new tests. The exception is automated regression testing, where repeating the same tests is valuable because the goal is to confirm nothing has broken.
29

List the seven testing principles in CTFL v4.0.

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1) Testing shows the presence, not the absence, of defects. 2) Exhaustive testing is impossible, so use test techniques, prioritisation and risk. 3) Early testing saves time and money. 4) Defects cluster together in a few components. 5) Tests wear out, so update them or write new ones. 6) Testing is context dependent. 7) Absence-of-defects fallacy: a defect-free system can still fail if it does not meet user needs.
30

Explain equivalence partitioning and its coverage.

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Equivalence partitioning divides data into partitions whose values are expected to be processed the same way, so one value per partition is enough. Partitions can cover inputs, outputs, configuration items or time, and include valid and invalid partitions. They must be non-empty and must not overlap. Coverage is partitions exercised divided by partitions identified. With several inputs, Each Choice coverage requires every partition of every input to be used at least once.

Frequently asked questions

What happens in the ISTQB telephonic interview round?

The telephonic or screening round is a 15-30 minute call with a recruiter or engineer. It checks your basics, your CV and whether you can explain ISTQB concepts clearly without a screen to point at.

How do I clear the telephonic interview round?

Keep your CV in front of you and be ready to explain every line on it. Answer in short, clear sentences; there is no whiteboard, so structure matters. Take the call somewhere quiet and confirm the time in advance.

Which round comes next?

A typical order is online assessment, telephonic screening, one or two technical rounds, a managerial round and HR. Use the other round pages to practise each stage.

Practise every interview round

Online Assessment questionsTechnical Round questionsManagerial Round questionsRapid-Fire questionsHR & behavioural questionsFull mock interview

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Company-wise ISTQB questionsExperience-wise ISTQB questionsRole-wise ISTQB questionsCity-wise ISTQB questionsMost asked ISTQB questionsScenario-based questionsPractical / hands-on questionsHR & behavioural questionsISTQB mock interviewOnline assessment questionsTechnical round questionsManagerial round questionsISTQB topic sheets