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Medium ISTQB Interview Questions

95 medium questions with answers. Applied questions that check whether you can use the concepts on real work.

Topics in the medium set

White-Box, Experience and Collaboration-Based Testing: 14 Static Testing: 13 Fundamentals of Testing: 12 Defect and Configuration Management: 12 Test Tools and Exam Preparation: 12 Testing Throughout the SDLC: 11 Black-Box Test Techniques: 11 Managing the Test Activities: 10
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01

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.
02

How is test analysis different from test design?

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Test analysis answers 'what to test': it analyses the test basis, identifies testable features, defines and prioritises test conditions, and evaluates the test basis for defects. Test design answers 'how to test': it turns test conditions into test cases, identifies coverage items, defines test data requirements and designs the test environment. Example: the condition 'login with a locked account' becomes, in design, a case with exact inputs and the expected error message.
03

What is testware? Give examples from different test activities.

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Testware is any work product created during the test process. Examples: test plan and risk register from planning; progress reports and control directives from monitoring and control; prioritised test conditions from analysis; test cases, test charters and coverage items from design; test procedures, automated scripts, test suites and test data from implementation; test logs and defect reports from execution; and the test completion report with lessons learned from completion.
04

Why is traceability between the test basis and testware important?

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Traceability links test basis items such as requirements, risks and user stories to test conditions, test cases, results and defects. It lets teams measure coverage, assess the impact of changes, support audits in regulated domains and report progress in business terms, for example 'requirement R12 has three passed tests and one open defect'. When a requirement changes, traceability shows exactly which tests must be updated or re-run.
05

What is the difference between the test management role and the testing role in CTFL v4.0?

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v4.0 describes roles, not job titles. The test management role owns the test process, the test team and leadership of test activities, mainly planning, monitoring and control, and completion. The testing role owns the engineering side: test analysis, design, implementation and execution. One person can hold both roles, and in Agile teams some management tasks are done by the team while cross-team coordination may sit with a test manager.
06

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.
07

A manager says, 'Testing found zero defects in this release, so the software is defect-free.' How do you respond?

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Testing shows the presence of defects, not their absence, so finding none only reduces the probability of undiscovered defects. I would also raise the absence-of-defects fallacy: did our tests cover real user needs? I would share coverage data, untested risk areas and whether our tests may have worn out. A more accurate statement is 'no defects were found within the agreed coverage and risk scope'.
08

Your manual regression suite has not found a new defect for several releases. What do you do?

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This points to the 'tests wear out' principle. I would review the suite against recent changes and defect data, refresh test data and steps, add tests for new features and risky areas, and run exploratory sessions to find new kinds of defects. Stable regression checks are still worth keeping and automating, because their job is to confirm unchanged areas still work, not to discover new defects.
09

Derive test conditions for the requirement 'Users can transfer up to 50,000 rupees per day.'

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Read the test basis and list testable aspects. Conditions: a transfer within the limit succeeds; a transfer of exactly 50,000 succeeds; a transfer above 50,000 is rejected with a clear message; several transfers in one day are added together against the limit; the limit resets the next day; zero or negative amounts are rejected. Prioritise them by risk, then design test cases with exact amounts using boundary value analysis.
10

How do you perform a simple root cause analysis on a production failure?

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Collect the failure details and logs, reproduce the issue and identify the defect. Then ask 'why' repeatedly until you reach a process cause. Example: a wrong discount was shown; why? the code used an old rule; why? the requirement changed without notice; why? there was no change review step. Action: add change notifications and a review step. Fixing root causes prevents whole families of similar defects.
11

Tell me about a time you found an important defect. How did you report it?

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Situation: while testing our final-year e-commerce project, I found checkout accepted expired coupon codes. Task: report it clearly before the demo. Action: I reproduced it three times and logged clear steps, expected and actual results, screenshots and the coupon data, and marked severity high because it meant revenue loss. Result: the developer fixed it within a day, and I added a regression test for coupon expiry.
12

Describe a situation where a developer rejected your defect. How did you handle it?

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Situation: a developer marked my defect 'works as designed'. Task: resolve it without conflict. Action: I re-read the user story, attached the acceptance criteria that contradicted the behaviour, and discussed it calmly with the developer and product owner, focusing on user impact rather than blame. Result: the product owner confirmed it was a defect, and we clarified the story wording so similar confusion did not happen again.
13

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.
14

Compare TDD, ATDD and BDD.

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All three are test-first approaches. In TDD, developers write a failing unit test, write code to pass it, then refactor. In ATDD, acceptance tests are derived from acceptance criteria with the team and business before development starts. In BDD, desired behaviour is written as Given/When/Then scenarios in natural language that stakeholders understand and that can be turned into executable tests. All three support shift-left.
15

What are the benefits and risks of DevOps for testing?

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DevOps joins development and operations through a CI/CD pipeline. Benefits for testing: fast feedback on code quality, shift-left through automated component tests and static analysis on every commit, stable environments through automation, more visibility of non-functional qualities and less repetitive manual work. Risks: the pipeline must be defined and maintained, CI/CD tools must be set up, and automation needs extra resources. Manual testing from the user's perspective is still needed.
16

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.
17

How does component integration testing differ from system integration testing?

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Component integration testing focuses on interfaces between components of the same system and is usually done by developers or testers who know the architecture, often with stubs and drivers. System integration testing focuses on interfaces with other systems and external services, such as payment gateways or government APIs, and needs production-like environments. Incremental integration, top-down or bottom-up, is preferred over big-bang because it localises defects.
18

You join a Scrum team with two-week sprints. What testing activities would you do during a sprint?

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I would join backlog refinement to review stories and acceptance criteria, help estimate test effort in sprint planning, write acceptance tests early, pair with developers on automation, test each story as soon as it is ready, keep regression running in the CI pipeline, run exploratory sessions on new features and share testing feedback in the retrospective. Testing runs continuously rather than at the end of the sprint.
19

A production hotfix must go live in three hours. How do you decide what to test?

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I would do a quick impact analysis to see what the change touches, run confirmation tests for the defect, then a risk-based regression subset covering the changed module, its integrations and critical business flows like login and payment. I would use the automated smoke suite in the pipeline, record what was not covered, and plan fuller regression in the next regular release.
20

Write a BDD scenario for locking an account after three failed login attempts.

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Feature: Account lockout Scenario: Lock account after three failed attempts Given a registered user with an active account When the user enters a wrong password 3 times in a row Then the account is locked And the message 'Account locked. Try again after 30 minutes' is shown Given sets the context, When is the action and Then is the expected outcome.
21

Show the TDD red-green-refactor cycle with a small example.

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# Red: write a failing test first def test_discount(): assert discount(1000) == 100 # Green: simplest code that passes def discount(amount): return amount * 0.10 # Refactor: improve design, test stays green RATE = 0.10 def discount(amount): return round(amount * RATE, 2) Repeat the cycle for each new behaviour, such as no discount below 500.
22

Tell me about a time testing was squeezed at the end of a sprint. What did you do?

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Situation: stories reached me only in the last two days of each sprint. Task: stop testing from being a bottleneck. Action: I proposed writing acceptance criteria and test cases during refinement, asked developers to merge smaller stories earlier, and automated API checks in the CI pipeline. Result: within three sprints, carried-over stories fell from five to one, and the team added early testing to its definition of done.
23

Describe how you convinced a team to adopt shift-left testing.

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Situation: our releases had many defects traced to unclear requirements. Task: reduce them without slowing delivery. Action: I showed data that about 40 percent of defects started in requirements, piloted requirement reviews and three-amigos sessions in one team, and tracked the results. Result: requirement-related defects dropped by roughly half over two releases, and other teams adopted the practice.
24

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.
25

What types of defects are typically found by static testing?

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Requirements defects such as inconsistencies, ambiguities, contradictions, omissions and duplicates; design defects like inefficient database structures or poor modularisation; coding defects such as variables with undefined values, unreachable or duplicated code and excessive complexity; deviations from standards; incorrect interface specifications; security vulnerabilities like buffer overflows; and gaps in test coverage, such as missing tests for an acceptance criterion.
26

Describe the activities of the review process in CTFL v4.0.

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Planning defines scope, purpose, quality characteristics, exit criteria, effort and timeframe. Review initiation ensures everyone has access and is ready. In individual review, each reviewer assesses the work product and logs anomalies, recommendations and questions. Communication and analysis discusses anomalies and decides their status and actions. Fixing and reporting creates defect reports, the author fixes them, and results are reported against exit criteria.
27

Compare the four review types in CTFL v4.0.

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An informal review has no defined process or formal output and aims to detect anomalies. A walkthrough is led by the author and aims to educate, build consensus, generate ideas and detect anomalies. A technical review is done by technically qualified reviewers led by a moderator, aiming at consensus and technical decisions. An inspection is the most formal, follows the full process, collects metrics and aims to find the maximum number of anomalies.
28

What are the success factors for reviews?

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Define clear objectives and measurable exit criteria; pick a review type that fits the objective, work product and people; review small chunks so reviewers stay focused; give feedback to authors so they improve; allow enough preparation time; secure management support; make reviews part of the culture to promote learning; and train participants for their roles. Review results must never be used to evaluate the performance of individuals.
29

In a review, what is the difference between an anomaly and a defect?

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Reviewers log anomalies: observations that differ from what they expected. Not every anomaly is a defect; some turn out to be misunderstandings, open questions or improvement suggestions. During communication and analysis the team decides each anomaly's status, owner and required action, and confirmed ones become defects for the author to fix. This keeps reviews constructive instead of treating every comment as the author's mistake.
30

The requirements say the system must be 'fast' and 'user-friendly'. What do you do?

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I would log these as anomalies in a review because they are not testable. I would ask stakeholders for measurable criteria, for example 'search results appear within 2 seconds for 95 percent of requests at 1,000 concurrent users' and 'a new user completes registration in under three minutes without help'. Testable requirements make test design, acceptance and sign-off objective and prevent disputes later.
31

A review meeting turns into people blaming the author. How do you handle it as moderator?

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I would refocus the discussion on the work product, not the person, remind everyone of the review objectives, and record the anomaly neutrally. Afterwards I would speak privately with the people involved. To prevent repeats, I would set ground rules, train participants and make sure review results are never used to judge individuals. Authors in a safe culture share work openly, so reviews find more defects.
32

A static analysis tool reports 2,000 warnings on legacy code. What is your approach?

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I would not try to fix everything at once. First, tune the rule set to remove irrelevant rules and false positives. Then classify warnings by severity and fix security issues and likely defects first. I would set a quality gate that blocks only new issues in changed code, so the codebase improves gradually. Trend reports each sprint show management steady progress.
33

Walk through the steps of running a technical review of a design document.

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Plan: define scope, objective and exit criteria and choose reviewers with the right expertise. Initiate: share the document, checklist and timeline. Individual review: each reviewer logs anomalies in a shared tool. Communication and analysis: the moderator runs the meeting, the team discusses anomalies and agrees actions. Fixing and reporting: the author updates the document, defects are tracked, and results are checked against exit criteria.
34

Show two defects a static analysis tool can find without running the code.

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def get_discount(amount): if amount > 1000: rate = 0.1 return amount * rate # rate undefined when amount <= 1000 def old_helper(): return 0 print('done') # unreachable code The tool flags a possibly undefined variable, a data flow anomaly, and unreachable code. Both are found statically, before any test is executed.
35

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.
36

How did you give feedback on a senior colleague's document that had many issues?

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Situation: a senior architect's design missed several error-handling flows. Task: give feedback respectfully. Action: I grouped comments by theme, framed them as questions with concrete examples, noted the strong sections, and offered to discuss in person rather than only posting comments. Result: he accepted most points, appreciated the clear feedback, and later invited me to review his designs earlier.
37

What is the difference between 2-value and 3-value boundary value analysis?

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BVA applies to ordered partitions. In 2-value BVA each boundary has two coverage items: the boundary value and its closest neighbour in the adjacent partition. In 3-value BVA there are three: the boundary and both neighbours. For a valid range 18 to 60, 2-value gives 17, 18, 60, 61, and 3-value gives 17, 18, 19, 59, 60, 61. 3-value is stricter and can catch defects like 'x == 18' written instead of 'x >= 18'.
38

How does decision table testing work, and how is coverage measured?

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Decision tables model combinations of conditions and the resulting actions, which suits business rules. Each column is a rule: one combination of conditions with its actions. With n Boolean conditions, a full table has 2 to the power n columns. Coverage items are the feasible columns, so coverage is exercised columns divided by feasible columns. Tables can be minimised by merging columns where a condition does not affect the outcome, shown with a dash.
39

A field accepts integers from 5 to 15. List the 3-value BVA test values.

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In 3-value BVA, each boundary gives the boundary value plus both neighbours. Lower boundary 5 gives 4, 5 and 6. Upper boundary 15 gives 14, 15 and 16. So the six values are 4, 5, 6, 14, 15 and 16. Compared with 2-value BVA (4, 5, 15, 16), the extra values 6 and 14 help detect mistakes in comparison operators inside the range.
40

Payment type has 3 partitions (card, UPI, wallet) and customer type has 2 (new, existing). What is the minimum number of tests for Each Choice coverage?

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Each Choice coverage needs every partition from each input used at least once, and one test can cover one partition of each input at the same time. So the minimum equals the largest number of partitions: 3. Example tests: card with new, UPI with existing, wallet with new. Covering all combinations would need 3 x 2 = 6 tests, which is not required for Each Choice.
41

Build a decision table for a loan rule: approve if salary is at least 30,000 and credit score is at least 700; refer if only one is met; otherwise reject.

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Conditions R1 R2 R3 R4 Salary >= 30000 T T F F Score >= 700 T F T F Actions Approve X - - - Refer to officer - X X - Reject - - - X Two Boolean conditions give 2 x 2 = 4 rules, so 4 test cases give 100 percent decision table coverage.
42

Marks from 0 to 100 give: 0-39 fail, 40-59 pass, 60-100 distinction. How many partitions and 2-value boundary values are there?

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Valid partitions: 0-39, 40-59 and 60-100, plus two invalid partitions: below 0 and above 100, so 5 partitions. Boundaries in 2-value BVA: -1, 0, 39, 40, 59, 60, 100 and 101, which is 8 values. Five tests give 100 percent EP coverage, and eight tests give 100 percent 2-value boundary coverage. Note that output partitions like fail, pass and distinction also guide the partitioning.
43

Free shipping applies for orders of 499 rupees or more, otherwise a fee of 40 applies. Design tests using EP and BVA.

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Partitions: 0 or less is invalid, 1 to 498 pays 40, and 499 or more ships free. EP tests: 0 rejected, 250 pays 40, 800 free. 2-value BVA adds 0 and 1 at the lower edge and 498 and 499 at the free shipping boundary. Combined minimal set: 0, 1, 250, 498, 499 and 800, each with the expected fee clearly stated.
44

Discount depends on customer type (regular, gold, platinum) and whether the order exceeds 1,000 rupees. How many rules does the full decision table have?

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When conditions are not Boolean, multiply the number of values of each condition. Customer type has 3 values and the order condition has 2, so the full table has 3 x 2 = 6 rules. Each rule becomes one test case for 100 percent decision table coverage. If, for example, platinum always gets the same discount regardless of amount, those two columns can be merged, giving 5.
45

An order can be placed, shipped, delivered, cancelled or returned. How would you test this workflow?

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State transition testing fits because behaviour depends on the current state and events. I would draw the diagram, for example placed to shipped, shipped to delivered, placed to cancelled, delivered to returned, and build a state table. Tests cover every valid transition and attempt invalid ones, such as cancelling a delivered order or returning an undelivered one, checking the system rejects them correctly.
46

A developer says one value per partition is enough. Why might you still add boundary tests?

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Equivalence partitioning assumes all values in a partition behave the same, but many defects occur at the edges, where developers write '>' instead of '>=' or use the wrong limit. One middle value like 35 in an 18 to 60 range will never reveal these. Boundary value analysis adds tests at 17, 18, 60 and 61, so the two techniques together give good coverage with few tests.
47

Tell me about a time a test design technique helped you find a defect.

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Situation: I was testing a scholarship form where students aged 17 to 25 were eligible. Task: design efficient tests for the age rule. Action: I applied boundary value analysis and tested 16, 17, 25 and 26. Result: 25 was wrongly rejected because the code used 'less than 25'. The developer fixed it, and I shared the BVA checklist with the team so others used it too.
48

What is branch testing and how is branch coverage measured?

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A branch is a transfer of control between two nodes in the control flow graph. Branches can be unconditional, like straight-line code, or conditional, like the true and false outcomes of an if or the cases of a switch. Branch coverage = branches exercised / total branches x 100. Branch testing designs tests so that every branch, including the hidden false path of an if without else, is exercised.
49

Why does 100 percent branch coverage guarantee 100 percent statement coverage, but not the other way round?

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Every statement lies on at least one branch, so exercising all branches executes all statements. The reverse fails when a decision has an empty outcome. Example: 'if x > 10: print(big)' followed by 'print(done)'. One test with x = 15 runs every statement, giving 100 percent statement coverage, but the false branch is never taken, so branch coverage is only 50 percent. This is called subsumption.
50

What is the value of white-box testing?

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White-box testing considers the whole implementation, so it can find defects even when the specification is vague, outdated or incomplete. Coverage gives an objective measure of thoroughness. It can also be used in static testing, for example dry runs of code or pseudocode. Its main weakness is that it cannot detect omissions: if a requirement was never implemented, no white-box test will notice it.
51

Explain collaborative user story writing, the 3 Cs and INVEST.

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User stories are written collaboratively by business, development and testing. The 3 Cs are Card (the medium describing the story), Conversation (how the story will be used, documented or verbal) and Confirmation (the acceptance criteria). A good story follows INVEST: Independent, Negotiable, Valuable, Estimable, Small and Testable. If stakeholders cannot say how to test a story, it is probably unclear or does not reflect real value.
52

What formats can acceptance criteria take?

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The two common formats are scenario-oriented, such as the Given/When/Then style used in BDD, and rule-oriented, such as a bullet-point verification list or a tabulated input-output mapping. Acceptance criteria define the scope of the story, reach consensus among stakeholders, describe positive and negative scenarios, serve as the basis for acceptance testing and support accurate planning and estimation. Teams can also use other formats as long as criteria are well defined and clear.
53

Find the minimum tests for 100 percent statement and branch coverage of this code.

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read(x) if x > 10: print('big') print('done') Statement coverage: one test with x = 15 executes every statement, so 1 test. Branch coverage: the if has a true and a false outcome, so tests with x = 15 and x = 5 are needed, 2 tests.
54

How many tests are needed for full statement and branch coverage of this nested code?

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if a > 0: if b > 0: s1 else: s2 else: s3 Statement coverage needs 3 tests, because s1, s2 and s3 are on different paths. Branch coverage also needs 3: (a > 0, b > 0), (a > 0, b <= 0) and (a <= 0). With full if-else structures, both criteria need the same number of tests.
55

Find the minimum tests for statement and branch coverage when there are two independent if statements in sequence.

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if a > 0: s1 if b > 0: s2 Statement coverage: one test with a = 1 and b = 1 runs s1 and s2, so 1 test. Branch coverage: each if needs a true and a false outcome. Tests (a = 1, b = 1) and (a = 0, b = 0) cover all four branches, so 2 tests.
56

Write a test charter for an exploratory session on a checkout page.

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Charter: Explore the checkout page with different coupon and payment combinations to discover pricing and rounding errors. Time box: 60 minutes. Focus areas: coupon stacking, expired coupons, quantity changes after applying a coupon, currency rounding, and using the browser back button. Record test ideas, defects, questions and areas covered. Debrief with the test lead after the session to agree next charters.
57

Your tests achieved 100 percent branch coverage, yet users reported a defect. How is that possible?

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Coverage shows which code was executed, not that the code is correct or complete. The defect may come from a missing requirement that was never coded, which white-box testing cannot detect; from specific data values not used in tests; from integration or environment issues; or from wrong expected results. Coverage is a useful measure of thoroughness, but it must be combined with black-box and experience-based techniques.
58

The requirements are incomplete and release is in two days. How do you test?

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I would use session-based exploratory testing. I would write short charters for the riskiest areas, agree priorities with the product owner, run time-boxed sessions, note defects and questions, and debrief after each session. I would add error guessing for common failure types and a quick checklist for critical flows, and report clearly which areas were covered and which risks remain.
59

The product owner writes vague acceptance criteria such as 'search should work well'. What do you do?

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I would suggest a short three-amigos session with the product owner and a developer. Together we would turn the vague criterion into testable ones, for example 'searching by product name returns matching items sorted by relevance', 'no results shows a helpful message' and 'results load in under 2 seconds'. Writing them as Given/When/Then scenarios makes them clear and ready for ATDD.
60

A new tester has no domain knowledge and no detailed test cases. How can checklists help, and what is the risk?

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A checklist of high-level conditions, such as validations, error messages, navigation and security basics, gives the new tester structure and consistency while learning the domain. Each run can vary slightly, which increases coverage. The risk is that checklists wear out as developers learn to avoid listed defects, so the team should update them with new defect patterns and pair the tester with an experienced colleague.
61

Tell me about an exploratory testing session that found a critical defect.

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Situation: a ticket booking app had passed all scripted tests. Task: run a one-hour exploratory session on seat selection. Action: I tried quick double taps, switching networks and booking the same seat from two devices. Result: two users could book the same seat. I logged a detailed report with videos, it was fixed before release, and concurrency tests were added to the regression suite.
62

How does a tester contribute to release and iteration planning?

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In release planning, testers help write testable user stories and acceptance criteria, take part in product and quality risk analyses, estimate test effort for stories, define the test approach and plan release testing. In iteration planning, they join detailed risk analysis of stories, check testability, break stories into testing tasks, estimate testing effort and identify the functional and non-functional aspects to test.
63

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.
64

What test case prioritisation strategies are there?

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Risk-based prioritisation orders tests by the results of risk analysis, running tests for the highest risks first. Coverage-based prioritisation orders by coverage, running tests that achieve the most coverage first; additional coverage prioritisation picks each next test by the extra coverage it adds. Requirements-based prioritisation follows the priorities of requirements set by stakeholders. Dependencies can force a lower-priority test to run first.
65

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.
66

What is the difference between a test progress report and a test completion report?

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A test progress report is produced regularly during testing, for example daily or per sprint. It covers the period, progress against plan, impediments, metrics, new or changed risks and planned work. A test completion report is prepared at the end of a test level, iteration or project. It summarises testing, evaluates quality against the plan, lists deviations, unmitigated risks, open defects, metrics and lessons learned.
67

Calculate a three-point estimate where optimistic is 6, most likely is 9 and pessimistic is 18 person-days.

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E = (a + 4m + b) / 6 = (6 + 4 x 9 + 18) / 6 = (6 + 36 + 18) / 6 = 60 / 6 = 10 person-days SD = (b - a) / 6 = (18 - 6) / 6 = 2 Report the estimate as 10 +/- 2 person-days, which gives a range of 8 to 12.
68

How do you prioritise risks using a likelihood and impact matrix?

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Score each risk for likelihood and impact on a scale such as 1 to 5, and multiply to get the risk level. Example: wrong interest calculation, likelihood 3 and impact 5, level 15; slow report export, likelihood 4 and impact 2, level 8; spelling errors, 4 and 1, level 4. Test the highest levels first and most deeply, using more rigorous techniques and earlier test execution.
69

Your CI pipeline takes two hours because most automated tests are UI tests. What do you suggest?

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The suite looks like an inverted test pyramid. I would push checks down: move business logic checks to unit tests, cover service rules with API tests, and keep only a small set of end-to-end UI tests for critical user journeys. I would also run tests in parallel and split suites into a fast smoke stage and a fuller nightly run. Feedback becomes faster and tests less flaky.
70

How do you report test status to non-technical stakeholders?

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I focus on decisions they need to make. I use a short dashboard: overall status in plain words, coverage of key requirements, open critical defects and their business impact, top risks with mitigation, and what is needed from them. I avoid jargon, use simple charts and trends, and keep detailed data available for anyone who wants it. Different audiences may need different levels of detail.
71

Tell me about a time you delivered testing under a very tight deadline.

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Situation: a regulatory change had to go live in five days. Task: test it without missing critical risks. Action: I ran a quick risk analysis with the product owner, focused on calculation rules and reports, automated repetitive data checks, and gave daily status updates. Result: we released on time with no production defects in high-risk areas, and lower-risk cosmetic issues were fixed in the next sprint.
72

What are false positives and false negatives in testing?

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A false positive is a test result that reports a defect when none exists, for example a test failing because of wrong test data or an unstable environment. A false negative is a test that passes even though a defect is present, so the defect is missed. False positives waste time and reduce trust in tests; false negatives are more dangerous because defects escape to production.
73

How does configuration management support testing?

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Configuration management identifies, controls and tracks work products such as test plans, test cases, scripts, test results, test data, environments and the test object itself. It ensures all configuration items are uniquely identified, version controlled, tracked for changes and related to each other so traceability is kept. Baselines can only be changed through formal change control. This lets testers know exactly which build and testware versions were tested.
74

Why is not every failed test a defect in the software?

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A failure can be caused by the test itself or the environment, not the test object. Common causes include wrong expected results, outdated test data, incorrect test scripts, misconfigured environments, network issues or unavailable third-party services. CTFL v4.0 therefore talks about anomalies, which are analysed before being reported as defects. Logging every failure as a defect without analysis creates false positives and wastes developer time.
75

A developer says your defect cannot be reproduced. What do you do?

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I would re-check that I can reproduce it, then add missing details: exact build version, environment, browser or device, user role, test data, timestamps, logs and a screen recording. I would check whether it is intermittent and note the frequency. If needed, I would reproduce it live with the developer. If it truly cannot be reproduced, we can keep it open with monitoring rather than close it.
76

Give an example of a high-severity low-priority defect and a low-severity high-priority defect.

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High severity, low priority: the app crashes when exporting a report in a legacy format that almost nobody uses; the impact is severe but rarely triggered, so it can wait. Low severity, high priority: the company logo is misspelled on the home page before a major launch; functionality is unaffected, but brand impact makes it urgent. Severity reflects impact, priority reflects business urgency.
77

Your defect tracker is full of duplicate defects from several testers. How do you fix this?

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I would set up a short daily triage to merge duplicates and link them to one master defect. Testers should search existing defects by module and keywords before logging, and use clear titles in a standard format such as 'Module - action - result'. Defined components and labels make searching easier. Tracking duplicate rates also shows whether the guidance is working.
78

Ten automated tests fail overnight, but the cause is an expired SSL certificate in the test environment. How should this be reported?

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These failures are caused by the environment, not the test object, so they should not be logged as product defects. I would raise one environment issue with the infrastructure team, mark the test results as blocked or environment failure, and re-run after the certificate is renewed. I would also suggest monitoring certificate expiry so the same false positives do not recur.
79

A defect you closed last week appears again in a new build. What could be the cause and what do you do?

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Possible causes include a code merge that overwrote the fix, a fix made only in one branch, or a deployment of an older artefact. I would re-open the defect with evidence and the build numbers, ask the team to check version control history, and add an automated regression test for the defect so it is caught immediately if it returns again.
80

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.
81

A module of 15,000 lines of code has 45 defects. Calculate its defect density and explain how you would use it.

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Defect density = defects / size = 45 / 15 KLOC = 3 defects per KLOC. If other modules average 1 defect per KLOC, this module is a defect cluster, so I would increase test depth there, ask for a code review or refactoring, and add more regression tests. Compare density only across similar code, because language and complexity affect the numbers.
82

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.
83

Your manager asks you to lower the severity of a defect to meet release targets. How do you respond?

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Situation: before a release, my manager wanted a payment defect marked minor. Task: stay honest without creating conflict. Action: I explained the actual impact with data, how often it occurred and affected users, and suggested keeping severity accurate while lowering priority if the business accepted the risk, with a workaround documented. Result: the manager agreed, and the risk was recorded transparently.
84

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.
85

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.
86

What changed in CTFL v4.0 compared with the 2018 syllabus?

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v4.0 added Agile and DevOps content: the whole team approach, test-first approaches like TDD, ATDD and BDD, shift-left, retrospectives, collaboration-based test approaches, the test pyramid and testing quadrants. It renamed the pesticide paradox to 'tests wear out', removed use case testing and decision coverage, focused white-box testing on statement and branch coverage, and described test roles instead of job titles.
87

How are CTFL v4.0 exam questions distributed across chapters?

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Approximately: Chapter 1, Fundamentals of Testing, 8 questions; Chapter 2, Testing Throughout the SDLC, 6; Chapter 3, Static Testing, 4; Chapter 4, Test Analysis and Design, 11; Chapter 5, Managing the Test Activities, 9; Chapter 6, Test Tools, 2. Chapters 4 and 5 carry half the marks and include most K3 questions, so practise techniques and estimation thoroughly.
88

An exam question asks for the 'best' answer and two options seem correct. How do you decide?

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Re-read the stem for keywords such as 'most likely', 'best', 'first' or 'not'. Compare both options strictly against the syllabus wording, not your company's practice. Often one option is partly true or too absolute, using words like 'always' or 'guarantees'. Choose the option that fully matches the syllabus definition. Practising official sample exams builds this habit.
89

Your automated regression suite fails randomly, and the team no longer trusts it. What do you do?

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Flaky tests are a known automation risk. I would quarantine flaky tests so they do not block the pipeline, then find the causes: hard-coded waits, shared test data, test order dependency or unstable environments. Fixes include explicit waits, independent test data, isolated environments and retries only for known infrastructure issues. I would track the flaky rate and return fixed tests to the main suite.
90

You have three years of testing experience and three weeks to prepare for CTFL. How do you plan?

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Experience helps, but the exam follows syllabus wording, not company practice. Week 1: read chapters 1 to 3 and the glossary terms in each learning objective. Week 2: study chapters 4 to 6, practise BVA, decision tables, state transitions, coverage and estimation calculations. Week 3: take timed official sample exams, analyse every wrong answer against the syllabus, and revise weak chapters.
91

How should you answer 'select TWO' questions in the CTFL exam?

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Read the instruction carefully, because you must select exactly two options and usually get the point only if both are correct. Evaluate each option separately as true or false against the syllabus. Eliminate absolute statements and options that describe a different concept. If you are sure of one, compare the remaining options carefully. These questions appear in the exam, so practise them in sample papers.
92

How do you use the ISTQB glossary to prepare effectively?

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Each learning objective lists keywords that you must know. Make flashcards for them with the exact glossary definition and one example from your own work, such as 'test basis: the user story for checkout'. Review them daily with spaced repetition. Pay attention to similar terms, like test condition versus test case, and confirmation versus regression testing, because exams use them as distractors.
93

How do you learn from sample exams instead of just counting your score?

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After each timed attempt, review every question, including correct guesses. For each mistake, note the learning objective, the chapter and why the right option is correct in the syllabus text. Group mistakes by chapter to find weak areas, re-read those sections, and redo similar questions after a few days. Aim for consistent scores of 32 or more out of 40 before the real exam.
94

How has ISTQB knowledge helped you in your job?

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Situation: our team wrote test cases with no clear technique, and suites kept growing. Task: improve efficiency. Action: I applied equivalence partitioning and boundary value analysis to the form validations and used decision tables for pricing rules, removing redundant tests. Result: we cut the regression suite by about 30 percent while finding more boundary defects, and my lead asked me to train two juniors.
95

Tell me about a time you introduced a new tool to your team.

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Situation: test cases lived in spreadsheets and traceability was poor. Task: introduce a test management tool. Action: I compared options with the team, ran a two-week pilot on one module, migrated priority test cases, built simple dashboards and ran short training sessions. Result: the team adopted it within a month, and release reports that took a day now took an hour.

Frequently asked questions

Who should practise medium ISTQB questions?

Anyone with some hands-on practice: most real interview time is spent on medium questions like these.

How should I practise these?

Answer each question aloud before opening the answer, mark it as solved only when your answer matches the key idea, and save misses to Last-Minute Revision.

Other difficulty levels