ISTQB Mock Interview: 20 Questions in 50 Minutes

Entry criteria define preconditions for starting an activity, such as available resources, testware, a stable build and a test environment. Exit criteria define what must be achieved to finish, such as coverage reached, unresolved defect counts, defect density and passed tests. Running out of time or budget can also be a valid exit. In Agile, exit criteria are often called the Definition of Done and entry criteria for a story the Definition of Ready.

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.

Testing triggers failures caused by defects (dynamic testing) or finds defects directly in work products (static testing). Debugging is a development activity that reproduces a failure, diagnoses the root cause and fixes the defect. After the fix, testers run confirmation testing to check the fix and regression testing to check nothing else broke. In short, testing finds and reports problems, while debugging locates and removes them.

It is a misconception that verifying software thoroughly and fixing every found defect guarantees success. A system can pass every test against its specification and still be useless if the specification was wrong or the users' real needs were missed. That is why testing must include validation as well as verification, for example early review of requirements with business stakeholders and user acceptance testing before release.

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.

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.

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.

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.

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.

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.

Testing is context dependent. For a medical device I would use formal documented plans, high independence, strict traceability to requirements, demanding coverage targets and evidence for regulators. For a mobile game I would use lightweight plans, exploratory testing, beta users, automation of core flows and fast releases. Factors that drive the choice include risk, regulations, budget, time, team skills, the SDLC and the technical environment.

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'.

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.

I would bring data: track defects found in reviews and estimate what they would have cost if found in system testing or production. I would also make reviews lighter: smaller chunks, checklists, time-boxed sessions, asynchronous tool-based reviews and static analysis to automate routine checks. Matching the review type to each work product keeps the cost low, and sharing the savings usually wins support.

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.

Situation: escaped defects kept coming from untested code paths. Task: improve unit testing without slowing the team. Action: I showed coverage reports linking low-coverage modules to production defects, proposed a gate of 80 percent branch coverage on new code only, and helped write the first tests. Result: within two months coverage on changed code rose sharply and escaped defects in those modules fell.

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.

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.

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.