ISTQB ISTQB-CTFL - ISTQB Certified Tester Foundation Level (CTFL v4.0)

Defect clustering is a testing principle that states that a small number of modules contain most of the defects detected during pre-release testing, or are responsible for most of the operational failures. Defect clustering can be explained by Pareto’s principle (also known as the 80-20 rule), which states that approximately 80% of the problems are found in 20% of the modules. Defect clustering suggests a change to the current test strategy for the next test cycle, as it implies that more effort should be allocated to test the modules that have shown high defect density or criticality. Pesticide paradox is another testing principle that states that if the same tests are repeated over and over again, eventually they will no longer find any new defects. Pesticide paradox suggests a change to the current test strategy for the next test cycle, but not based on defect clustering, but rather on test diversity and coverage. Early testing is a testing principle that states that testing activities should start as early as possible in the software development life cycle and should be focused on defined objectives. Early testing does not suggest a change to the current test strategy for the next test cycle, but rather a proactive approach to prevent defects from occurring or propagating. Absence-of-errors fallacy is a testing principle that states that finding and fixing defects does not help if the system built is unusable and does not fulfill the users’ needs and expectations. Absence-of-errors fallacy does not suggest a change to the current test strategy for the next test cycle, but rather a focus on quality attributes and user requirements. Verified References: A Study Guide to the ISTQB® Foundation Level 2018 Syllabus - Springer, Chapter 1, page 9-10.

Comprehensive and Detailed In-Depth Explanation:

Equivalence partitioning (EP) divides input values into classes where test cases represent all possible values of each partition. The partitions in this scenario are:

≤7 (too cold → W)

8-21 (standstill → X)

22-29 (ideal → Y)

≥30 (too hot → Z)

Option C ({7,10,25,29}) covers all partitions by selecting representative values:

7 → Too cold (W)

10 → Standstill (X)

25 → Ideal (Y)

29 → Upper boundary of ideal (Y)

Other options do not cover all partitions adequately.

The choice of a software development lifecycle (SDLC) model is primarily influenced by the type of product being developed. Different products and project requirements may demand different SDLC models to address specific challenges and needs efficiently. For instance, a complex, safety-critical product might best be served by a Waterfall model due to its structured nature and phase dependencies, while a more iterative and incremental model might be suited for projects requiring frequent feedback and changes.

This answer is correct because product risks are risks that affect the quality of the software product, such as defects, failures, or non-compliance with requirements or standards. Project risks are risks that affect the project’s schedule, budget, resources, or scope, such as delays, cost overruns, skill gaps, or scope changes. In this case, [I] and [IV] are product risks, as they relate to the accessibility and security of the software product, which are quality attributes. [II] and [III] are project risks, as they relate to the delivery time and the test automation skills of the test team, which are project factors. References: ISTQB Glossary of Testing Terms v4.0, ISTQB Foundation Level Syllabus v4.0, Section 2.1.1.1

Comprehensive and Detailed In-Depth Explanation:

Independent testers provide a fresh perspective and are more likely to identify failures that developers might overlook due to their familiarity with the software (C). Independent testing helps avoid cognitive biases, improves defect detection, and enhances the overall quality assurance process. While A and D touch on related concepts, they do not directly define the benefit as well as C does. Option B highlights a potential challenge rather than a benefit.

Cost can be regarded as an exit criterion for testing, because it is a factor that affects the profitability and feasibility of the software product. Testing is an investment that aims to improve the quality and reliability of the software product, but it also consumes resources, such as time, money, and human effort. Therefore, testing should be planned and executed in a way that balances the cost and benefit of testing activities. Having cost as an exit criterion helps to avoid spending too much money on testing, which may result in an unprofitable product or a loss of competitive advantage. Cost can also help to prioritize and focus the testing efforts on the most critical and valuable features and functions of the software product. However, cost should not be the only exit criterion for testing, as it may not reflect the true quality and risk level of the software product. Other exit criteria, such as defect rate, test coverage, user satisfaction, etc., should also be considered and defined in the test plan.

The other options are incorrect, because they either deny the importance of cost as an exit criterion, or they make false or unrealistic assumptions about the cost of testing. Option B is incorrect, because the financial value of product quality can be estimated, for example, by using cost-benefit analysis, return on investment, or cost of quality models. Option C is incorrect, because going by cost as an exit criterion does not necessarily constrain the testing project or help achieve the desired quality level. Cost is a relative and variable factor that depends on the scope, complexity, and context of the software product and the testing project. Option D is incorrect, because the cost of testing can be measured effectively, for example, by using metrics, such as test effort, test resources, test tools, test environment, etc.

Covering all transitions at least once is the highest coverage criterion for state transition based test cases, because it ensures that every possible change of state is tested at least once. This means that all the events that trigger the transitions, as well as the actions and outputs that result from the transitions, are verified. Covering all transitions at least once also implies covering all states at least once, but not vice versa. Therefore, option D is not the highest coverage criterion. Option C is the lowest coverage criterion, because it only tests the initial and final states of the system or component, without checking the intermediate states or transitions. Option A is incorrect, because the coverage criteria for state transition based test cases can be determined and compared based on the number of transitions and states covered. References = CTFL 4.0 Syllabus, Section 4.2.3, page 49-50.

The following statements about risk-based testing are correct:

II) Tests should be prioritized to find tie critical detects as early as possible. Risk-based testing involves prioritizing tests based on risk level, which reflects both the likelihood and impact of defects or failures. Tests with higher risk level should be executed earlier than tests with lower risk level, in order to find and fix critical defects as soon as possible.

III) Non-testing activities may also help to reduce risk. Risk-based testing does not only involve testing activities, but also other activities that can help mitigate risks, such as reviews, inspections, audits, simulations or prototyping.