Explanation / Rationale

a) Is correct. The ‘tests wear out’ principle is concerned with the idea that repeating identical tests on unaltered code is unlikely to uncover novel defects and therefore, modifying tests may be essential. By using high-level test conditions to generate new tests each time, the tests will not be identical and should not ‘wear out’
b) Is not correct. The ‘absence-of-defects fallacy’ principle is concerned with ensuring that users’ needs are fulfilled even if lots of testing is done and no defects are found (i.e., validation is also necessary). The use of high-level test conditions to generate test cases and execute tests does not directly address this concern
c) Is not correct. The ‘early testing saves time and money’ principle is concerned with fixing defects early on to prevent the occurrence of subsequent defects in derived work products, thereby reducing costs and the likelihood of failures. This is typically addressed by starting testing (both static and dynamic) as early as possible, but this is not addressed by using high-level test conditions to generate test cases and execute tests
d) Is not correct. The ‘Defects cluster together’ principle is concerned with the distribution of defects in a system, which typically follows a Pareto distribution. The use of high-level test conditions to generate test cases and execute tests does not address this concern, which is typically addressed by risk-based testing

Explanation / Rationale

a) Is not correct. Dynamic testing does cause failures (from which defects can then be located and fixed). However, debugging is concerned with locating defects and fixing these defects. Therefore, debugging does not fix failures
b) Is not correct. Both testing and debugging contribute to improving the quality of the test object, so should really both be considered positively. Debugging is generally considered to be a positive activity as it is fixing something. Dynamic testing does involve intentionally causing the test object to fail, which is why some people consider it a negative activity, but that is a very narrow view (and not one typically held by testers). Both positive and negative test cases are possible. Positive test cases check that the test object correctly performs what it is supposed to do, while negative testing checks that the test object does not do what it is not supposed to do
c) Is correct. Testing determines that defects exist either directly through observation of the defect in reviews (or by a tool in static analysis), or indirectly by causing a failure in dynamic testing. Debugging is a separate activity from testing (normally performed by developers) and is concerned with locating defects (only for dynamic testing) and fixing the defects
d) Is not correct. The causes of defects are typically human errors. Testing finds defects either directly through static testing, or indirectly by causing failures in dynamic testing, and debugging fixes defects. So, testing does not find the cause of defects and debugging does not fix the causes of defects

Explanation / Rationale

a) Is not correct. The fundamental strength of white-box test techniques is that the entire software implementation is taken into account during testing
b) Is not correct. White-box coverage measures provide an objective measure of coverage and provide the necessary information to allow additional tests to be generated to increase this coverage
c) Is not correct. White-box test techniques can be used to perform reviews (static testing)
d) Is correct. This is the weakness of the white-box test techniques. They are not able to identify the missing implementation, because they are based solely on the test object structure, not on the requirements specification

Explanation / Rationale

a) Is not correct. The test pyramid model does not provide information about test priorities
b) Is correct. The test pyramid model shows that different tests have different levels of granularity
c) Is not correct. The test pyramid model is independent of coverage criteria
d) Is not correct. Test pyramid model does not show any relations between different tests

Explanation / Rationale

a) Is correct. It is important that testers are involved from the beginning of the software development lifecycle (SDLC). It will increase understanding of design decisions and will detect defects early.
b) Is not correct. Both developers and testers will have more understanding of each other's work products and how to test the code
c) Is not correct. End users will not help the testers in increasing the quality of defect reports; also, users usually do not participate in low-level testing levels like integration testing
d) Is not correct. Being certified does not automatically mean that the tester will be better in test design

Explanation / Rationale

Error guessing is about anticipating the errors, defects and failures based on the tester’s knowledge.
a) Is not correct. This is an example of anticipating the developer’s error
b) Is not correct. This is an example of anticipating the defect
c) Is correct. This is an example of a potential root cause of a defect, which is neither an error, defect nor failure, and difficult for the tester to anticipate
d) Is not correct. This is an example of anticipating a failure, perhaps based on experience of previous systems in this application domain

Explanation / Rationale

a) Is not correct. Risk management consists of risk analysis and risk control. Neither of these activities supports the reassembly of the files that made up the release, because these activities deal with risks, not with configuration items
b) Is not correct. Test monitoring is concerned with gathering information about testing. This information is used to assess test progress and to measure whether the test exit criteria or the test tasks associated with the exit criteria are satisfied, such as meeting the targets for coverage of product risks, requirements, or other acceptance criteria. Test control uses the information from test monitoring to provide, in the form of control directives, guidance and the necessary corrective actions to achieve the most effective and efficient testing. None of these activities deal with the management of configuration items
c) Is not correct. The whole-team approach builds on the tester’s skill to work effectively in a team context and to contribute positively to the team goals. So, it focuses on team-related issues, not on configuration items
d) Is correct. Configuration management provides a discipline for identifying, controlling, and tracking work products. Configuration management keeps a record of changed configuration items when a new baseline is created. Using configuration management, it is possible to revert to a previous baseline in order to reproduce previous test results

Explanation / Rationale

Consider:

i. Is true. Faster product release and faster time to market is an advantage of DevOps
ii. Is false. Typically, we need less effort for manual tests because of the use of test automation
iii. Is true. Constant availability of executable software is an advantage
iv. Is false. More regression tests are needed
v. Is false. Not everything is automated and setting up a test automation framework is expensive

Thus:
a) Is not correct
b) Is not correct
c) It is correct
d) Is not correct

Explanation / Rationale

a) Is not correct. In the whole-team approach, testers play a vital role by sharing their testing expertise with the team and guiding product development. They collaborate with other team members to achieve the desired quality levels and work with business representatives to create acceptance tests. Testers also partner with developers to determine the optimal test strategy and automation approaches
b) Is correct. By leveraging the diverse skill sets of each team member most effectively, the whole-team approach fosters superior team dynamics, promotes robust communication and collaboration, and generates a synergistic effect that benefits the entire project
c) Is not correct. The whole-team approach allows any team member with the requisite skills and knowledge to undertake any task, thus specialist team members are not an advantage of this approach
d) Is not correct. There is no specific guidance on the optimum size of teams using the whole-team approach, and there is no suggestion that larger teams are better

Explanation / Rationale

a) Is not correct. Assuming that testers could check the ease of changing the currency exchange system then it would be done by maintainability testing rather than maintenance testing, so this is not a trigger for maintenance testing
b) Is correct. A system modification (such as a fix or enhancement) is an example of a trigger for maintenance testing. The removal of the refund option of the currency exchange system was a fix that would lead to maintenance testing
c) Is not correct. If the agile team has started developing a user story that adds a new customer loyalty feature to the currency exchange system, then this will result in them testing the new feature, and then they would perform regression testing. No maintenance testing is required in this situation
d) Is not correct. Reconfiguration of the currency exchange system to support both the local language and English currency transactions is not a system modification, a change to the operational environment, or a system retirement, which are the three triggers for maintenance testing

Explanation / Rationale

a) Is not correct. Although it is correct to say that in Agile software development, some of the test management tasks may be handled by the Agile team itself, the testing role is not primarily the responsibility of a single individual from outside the team. Instead the testing is more likely to be performed by various team members following the whole-team approach
b) Is not correct. The test management role primarily involves activities related to test planning, test monitoring and control, and test completion. So, although this statement is partially correct, it is wrong to say that the testing role is primarily responsible for test monitoring and control
c) Is correct. In Agile software development, some of the test management tasks may be handled by the Agile team itself. However, for test activities that span multiple teams within an organization, test managers outside of the development team may perform these tasks
d) Is not correct. The test management role primarily involves activities related to test planning, test monitoring and control, and test completion, while the testing role is primarily responsible for the technical and engineering aspects of testing, such as test analysis, test design, test implementation, and test execution. Thus the test management role is not normally responsible for test analysis and test design, although it is correct to say that the testing role is primarily responsible for test implementation and execution

Explanation / Rationale

Exploratory testing is useful when there are few or inadequate specifications or there is significant time pressure on the testing. Exploratory testing is also useful to complement other more formal test techniques. Exploratory testing will be more effective if the tester is experienced, has domain knowledge and has a high degree of essential skills, like analytical skills, curiosity and creativeness.

Thus:
a) Is correct. Exploratory testing is useful when there are few or inadequate specifications or there is significant time pressure on the testing
b) Is not correct. Exploratory testing is not a black-box test technique
c) Is not correct. Exploratory testing is useful when the specifications are poorly written
d) Is not correct. Programming skills have nothing to do with exploratory testing in principle
e) Is correct. Exploratory testing will be more effective if the tester is experienced, has domain knowledge and has a high degree of essential skills, like analytical skills, curiosity and creativeness

Explanation / Rationale

a) Is not correct. Component testing (also called unit testing) involves testing individual components in isolation and is mostly verification against a specification, rather than validation against user needs. However, this testing is not normally performed by testers, as developers usually carry out this testing in their development environment
b) Is not correct. Component integration testing involves testing the interfaces and interactions between components and is mostly verification against a specification, rather than validation against user needs. However, this testing is not normally performed by testers, as developers usually carry out this testing
c) Is not correct. System integration testing examines the interfaces with other systems and external services and is mostly verification against a specification, rather than validation against user needs. This type of testing is also most often performed by testers
d) Is correct. Acceptance testing focuses on validating that the system meets the user's business needs and is ready for deployment. Ideally, this testing is carried out by the end users

Explanation / Rationale

a) Is correct. Checking that the sort function puts the elements of the list or array in ascending order is evaluating the functional correctness of the sort function, which is part of functional testing
b) Is not correct. Assessing whether the sort function meets its non-functional requirement to complete within one second is part of testing its performance efficiency, which is part of non-functional testing
c) Is not correct. Evaluating the ease with which the sort function can be modified from sorting ascending to sorting descending is testing its modifiability, a form of non-functional maintainability testing, which is part of non-functional testing
d) Is not correct. Assessing that the sort function still functions correctly when moved from a 32-bit to a 64-bit architecture is testing its adaptability, a form of portability testing, which is part of non-functional testing

Explanation / Rationale

Using the three-point estimation technique, the final estimate (E) is calculated as:

E = (a + 4*m + b) / 6,

where a is the most optimistic estimate, m is the most likely estimate, and b is the most pessimistic estimate.

Thus:
a) Is correct. In this case, the estimate for executing a single test case is:

E = (1h + 4*3h + 8h) / 6 = 3.5 hours

So, the total time needed for the tester to execute 4 test cases is:

3.5h * 4 = 14 hours

b) Is not correct
c) Is not correct
d) Is not correct

Explanation / Rationale

Considering:

Testing and quality assurance are not the same. Testing is the process consisting of all software development lifecycle (SDLC) activities, both static and dynamic, concerned with planning, preparation and evaluation of a component or system and related work products to determine that they satisfy specified requirements, to demonstrate that they are fit for purpose and to detect defects. Quality assurance is focused on establishing, introducing, monitoring, improving, and adhering to the quality-related processes.

Thus:
a) Is not correct
b) Is not correct
c) Is not correct
d) Is correct

Explanation / Rationale

We want to run test cases according to their priorities, but we also need to consider the dependencies.
If we only consider priorities, we want to first run TC 5 and TC 7 (highest priority), then TC 1, TC 3, and TC 4, and finally TC 2 and TC 6 (lowest priority).
However, in order to run TC 7, we need to first run TC 4.
In order to run TC 5, we need to run TC 4 and TC 2, but TC 2 is blocked by TC 1, which should be run prior to TC 2.
So, in order to run priority 1 test cases as early as possible, the first five test cases should be: TC 4 - TC 7 - TC 1 - TC 2 - TC 5.
Next, we need to run TC 3, because it has higher priority than TC 6.
Thus the full schedule will be TC 4 – TC 7 – TC 1 – TC 2 – TC 5 – TC 3 – TC 6.
So, the sixth test case will be TC 3.

Thus:
a) Is correct
b) Is not correct
c) Is not correct
d) Is not correct

Explanation / Rationale

a) Is correct. This test case is related to acceptance criteria 2 and 3, because we check if we can set price range (acceptance criterion 2) and if the results update dynamically after adjusting the price range filter (acceptance criterion 3)
b) Is not correct. This test case is not related to any of the acceptance criteria. It checks if the filter dynamically sets the default minimum and maximum price range, and not that a customer can do it
c) Is not correct. This test case is not related to any of the acceptance criteria. It checks the currency exchange feature, which is not discussed in this user story
d) Is not correct. This test case is not related to any of the acceptance criteria. It checks the application’s compatibility with different browsers, which is not discussed in this user story

Explanation / Rationale

a) Is not correct. DevOps enhances testing in several ways, such as by providing fast feedback on code quality, automated regression testing that minimizes regression risk, and promoting a shift-left approach with high-quality code submission and component tests. This is largely provided through continuous integration, where the developers submit component (unit) tests with their new code, which must pass for the code to be admitted to the build. Therefore, developers do need to complete component testin
b) Is correct. DevOps enhances testing in several ways, such as by providing fast feedback on code quality, automated regression testing that minimizes regression risk, and promoting a shift-left approach with high-quality code submission and component tests
c) Is not correct. DevOps enhances testing in several ways, such as by providing fast feedback on code quality, automated regression testing that minimizes regression risk, and promoting a shift-left approach with high-quality code submission and component tests. Testers do not attempt to treat developers and operations equally by spending more time on release testing, although a shift-right approach to testing (testing in production) may well be used
d) Is not correct. Automated processes like continuous integration/continuous delivery (CI/CD) in DevOps facilitate stable test environments and reduce the need for manual testing, however, there is a risk of overlooking the importance of manual testing, especially from a user's perspective

Explanation / Rationale

There are two equivalence partitions that are not yet covered, which correspond to “student discount” and “pensioner discount”.
a) Is not correct. CY – BY = 64, so these inputs correspond to the already covered “no discount” partition
b) Is correct. CY – BY = 65, so these inputs correspond to a partition that is not yet covered (“pensioner discount”)
c) Is not correct. CY – BY = –65, so these inputs correspond to the already covered “error message” partition
d) Is not correct. CY – BY = 18, so these inputs correspond to the already covered “no discount” partition
e) Is correct. CY – BY = 0, so these inputs correspond to a partition that is not yet covered (“student discount”)

Explanation / Rationale

a) Is not correct. It is often possible to use dynamic testing to cause a test object to fail in ways that could never be achieved by the users, such as by using fault injection. However, if the failure can never occur with real end users, then identifying it is not especially valuable as testing is ultimately aimed at improving the work product for the end users. Spending time testing for failures that cannot occur with real users is not an efficient use of a tester’s time
b) Is not correct. Static testing in the form of static analysis is used by developers to identify defects in their program code earlier than can be achieved through dynamic testing. Note, however, that static testing (and static analysis) is used to detect defects, not failures, which are found by dynamic testing. Thus it is the use of the term ‘failures’ that makes this an incorrect option
c) Is not correct. Static analysis directly detects anomalies in code, which may be defects, and this is normally for the developer, not the customer. The provision of evidence for release by the use of static analysis of elements that provide no output is nonsense
d) Is correct. Reviews are a form of static testing that can be applied from the very start of the software development lifecycle and are used to find defects that can be removed before subsequent development activities waste effort on faulty requirements. If the defects are not detected and removed early on, then when the defect is found derived work products, such as the design and code, will need to be changed as they were based on faulty requirements

Explanation / Rationale

The testware under consideration is a test charter

Test charters are the output from test design
Thus:
a) Is not correct
b) Is not correct
c) Is not correct
d) Is correct

Explanation / Rationale

a) Is not correct. Acceptance criteria are the conditions used to decide whether the user story is ready. They cannot show work progress
b) Is not correct. Defect reports inform about the defects. They do not show work progress
c) Is not correct. Test completion report can be created after the iteration is finished, so it will not show the progress continuously within an iteration
d) Is correct. Burndown charts are a graphical representation of work left to do versus time remaining. They are updated daily, so they can continuously show the work progress

Explanation / Rationale

a) Is correct. This principle means that if the same tests are repeated over and over again, eventually these tests no longer find any new defects. This is probably why the tests all passed in this release as well
b) Is not correct. This principle says about the mistaken belief that just finding and fixing a large number of defects will ensure the success of a system
c) Is not correct. This principle says that a small number of components usually contain most of the defects
d) Is not correct. This principle states that testing all combinations of inputs and preconditions is not feasible

Explanation / Rationale

The ‘exhaustive testing is impossible’ principle is concerned with the fact that it is not feasible to test every possible variation of test inputs in all different circumstances, except in trivial cases. Instead, testing utilizes test techniques, test case prioritization, and risk-based testing to sample from the set of possibilities and focus testing efforts.
a) Is not correct. The principle states that it is not feasible to test everything except in trivial cases. Testing everything would require testing every possible variation of test inputs in all different circumstances, which is generally infeasible as there will be a practically infinite number. Testing every possible specified output will not address this problem as the relationship between inputs and specified outputs can be different for each test object. Sometimes there may be a practically infinite number of possible specified outputs (e.g., when there are several variables representing real numbers), whereas at other times there may be just two specified outputs, such as with a single variable that can be either true or false
b) Is not correct. The principle states that it is not feasible to test every possible variation of test inputs in all different circumstances. This is because for non-trivial systems there is a practically infinite number. Therefore, in practice, documenting all possible test input variations would be impractical as it would take an infinite length of time
c) Is not correct. Starting testing as early as possible with reviews and other static testing approaches will not address the problem of there being too many possible test cases. The ‘early testing saves time and money’ principle is concerned with fixing defects early on to prevent the occurrence of subsequent defects in derived work products, thereby reducing costs and the likelihood of failures
d) Is correct. The use of equivalence partitioning and boundary value analysis to generate test cases is one way to address the principle as these test techniques provide a systematic way to derive a finite subset of all possible test cases

Explanation / Rationale

a) Is not correct. Most work products can be examined using some form of static testing, and a contract must be interpretable by humans and so could be reviewed, which is a form of static testing
b) Is not correct. Most work products can be examined using some form of static testing, and a test plan must be interpretable by humans and so could be reviewed, which is a form of static testing
c) Is correct. Most work products can be examined using some form of static testing; however it is not suitable for work products that are too complex for human interpretation and should not be analyzed by tools, and encrypted code is too complex for humans and if it is properly encrypted it will not be analyzable by most tools
d) Is not correct. Most work products can be examined using some form of static testing, and a test charter must be interpretable by humans and so could be reviewed, which is a form of static testing

Explanation / Rationale

a) Is not correct. While the sentence is true, it does not provide much value for the developer
b) Is correct. From the test results it seems that the system ignores duplicates and sorts the list disregarding the repetitions. This is probably the cause of failures in TC3, TC4, TC5. Such information may help the developer to find the defect and fix it more efficiently
c) Is not correct. The system does not fail in sorting negative numbers. The problem is rather in disregarding duplicates
d) Is not correct. The test cases TC3, TC4 and TC5 fail, but we aren’t aware that the test cases have any defects

Explanation / Rationale

a) Is not correct. Testers should review work products as soon as drafts are available to enable early testing as part of a shift-left approach. If they waited until the next development phase, then unnecessary development (and test) work could be started on unreviewed, flawed work products
b) Is correct. Testers should review work products as soon as drafts are available to enable early testing as part of a shift-left approach
c) Is not correct. Testers typically review work products that form the test basis as part of test analysis, not before test analysis and design
d) Is not correct. Testers should review work products as soon as drafts are available to enable early testing as part of a shift-left approach. Waiting until they are published means that any defects that could be found by tester review will be in the published document

Explanation / Rationale

a) Is not correct. We want to check that Special users have the rights of Regular users, so we need to test access rights for a Special user, not for a Regular user
b) Is not correct. We want to check that Special users have the rights of Regular users, so we need to test access rights for a Special user, not for a Regular user
c) Is not correct. There is no floor 5 described in the acceptance criteria. The test cases should not extend the scope of the user story. But even if we would like to perform negative testing, this test is not directly related to AC3
d) Is correct. This way we can check if a Special user can access floors which are accessible to a Regular user

Explanation / Rationale

According to the dependencies, SEARCH tests must be executed first, then VIEW tests, then ADD tests and, at the end, ORDER tests. Within each of these groups the order is determined by the priorities of the test cases.
So, TC1 must be executed first, then TC2, then TC4 followed by TC3, and then TC5 as the last one.
So, the ordering is: TC1, TC2, TC4, TC3, TC5.
Thus:
a) Is correct. TC3 will be the fourth test case executed
b) Is not correct
c) Is not correct
d) Is not correct

Explanation / Rationale

a) Is not correct. The test automation approach is defined by testers with the help of developers and business representatives
b) Is not correct. The test strategy is decided in collaboration with the developers
c) Is not correct. Testers, developers, and business representatives are part of the whole team approach
d) Is correct. Testers will work closely with business representatives to ensure that the desired quality levels are achieved. This includes supporting and collaborating with them to help them create suitable acceptance tests

Explanation / Rationale

a) Is not correct. In agile software development, deliverables are produced in each iteration, and the frequent delivery of increments necessitates extensive regression testing. Although some (or all) of this regression testing may be automated, the regression testing (automated or not) cannot be replaced by system test automation
b) Is correct. If a sequential development model is used, then early in the lifecycle no code is available for execution, and so during this time static testing (e.g., reviews) is performed. Later in the lifecycle, when code is available for execution, dynamic testing is possible. Note, however, that preparation for dynamic testing will often occur early in any software development lifecycle
c) Is not correct. If an iterative development model, like agile software development, is used, then component tests may well be used for regression testing for each iteration. In which case, there is a strong argument for automating these component tests, which will have to be run frequently, and there is unlikely to be a strong argument for developers performing these component tests manually
d) Is not correct. In most incremental development models, deliverables are produced in each increment, requiring both static and dynamic testing at all test levels for each increment delivered

Explanation / Rationale

Considering:

• Usability testing is in Q3 (1 – C)
• Component testing is in Q1 (2 – A)
• Functional testing is in Q2 (3 – B)
• Reliability testing is in Q4 (4 – D)

Thus:
a) Is correct
b) Is not correct
c) Is not correct
d) Is not correct

Explanation / Rationale

Test cases TC1, TC2, TC3 and TC4 cover, respectively, rules R2, R3, R7 and R6 in the decision table.
a) Is correct. The conditions “66-year-old”, “unregistered” and “no experience” match rule R4, which is not covered by the existing test cases, so after adding this test case, the decision table coverage will increase
b) Is not correct. The conditions “55-year-old”, “unregistered” and “2 years of experience” match rule R2, already covered by TC1. So adding this test case will not increase the coverage
c) Is not correct. The conditions “19-year-old”, “registered” and “5 years of experience” match rule R6, already covered by TC4. So adding this test case will not increase the coverage
d) Is not correct. The existing test cases cover only 4 out of 7 columns of the decision table. The coverage can be increased by adding test cases that cover yet uncovered columns, that is, R1, R4 and R5

Explanation / Rationale

a) Is not correct. QA concentrates on process improvement and implementation, using a preventive approach to avoid errors and defects, while testing is a form of QC that is used to detect defects
b) Is correct. QC aims to achieve appropriate levels of quality by focusing on identifying and correcting product defects. Testing is a significant part of QC and helps to uncover these defects
c) Is not correct. Although testing is a significant part of QC and helps to uncover defects, other (non-testing) techniques utilized in QC include formal methods like model checking and proof of correctness, as well as simulation and prototyping
d) Is not correct. QA concentrates on process improvement and implementation, using a preventive approach to avoid errors and defects, while testing is a form of QC that is used to detect defects

Explanation / Rationale

Consider:

i. It is a Project risk
ii. It is a Product risk
iii. It is a Product risk
iv. It is a Project risk
v. It is a Product risk

Thus:
a) Is correct
b) Is not correct
c) Is not correct
d) Is not correct

Explanation / Rationale

In branch testing the coverage items are branches, which are represented by the edges of a control flow graph. There are 8 edges in the control flow graph.
Thus:
a) Is not correct
b) Is not correct
c) Is correct
d) Is not correct

Explanation / Rationale

a) Is not correct. ‘The capability of generating test cases without access to the test basis’ is not possible. The generation of test cases by either testers or tools requires access to the test basis
b) Is not correct. ‘The achievement of increased coverage through more objective assessment’ is not a direct benefit of test automation. Test automation will provide more objective assessment of coverage, however that objective assessment will not increase the coverage. Only by using the results of the coverage to write further test cases can the coverage possibly be increased
c) Is not correct. ‘The increase in test execution times available with higher processing power’ is a contradictory statement as higher processing power would normally reduce execution times, and increased execution times are not a benefit as the testing would take longer
d) Is correct. The prevention of human errors through greater consistency and repeatability is a benefit of test automation as test automation cannot suffer from human errors. For instance, it means that tests are consistently derived from requirements, test data is created in a systematic manner, and tests are executed by a tool in the same order with the same frequency

Explanation / Rationale

Let us refer to the transitions with E1, …, E5 as in the picture. The variable N denotes the number of elements currently stored. Each “Add” event increases it by 1, and each “Remove” event decreases it by 1. Notice, that when the “Add” event occurs while being in the NOT FULL state, the state changes to FULL only if N=2. If N<2, the system stays in the NOT FULL state. If N=0, no “Remove” action is possible. Similarly, if N=3, no “Add” action is possible.

Test a) can be written as E1, E3, E3, E2, E4 (so covers 4 out of 5 valid transitions, achieving 80% valid transitions coverage).
Test b) is infeasible, because after the first three “Add” actions the system is in the FULL state and there is no valid transition going from FULL triggered by the “Add” event. After the first three transitions only 60% of valid transitions coverage is achieved.
Test c) can be written as E1, E2, E4, E5, E3 (so covers 5 out of 5 valid transitions, achieving 100% valid transitions coverage).
Test d) can be written as E1, E2, E4, E5, E4 (so covers 4 out of 5 valid transitions, achieving 80% valid transitions coverage).

Thus:
a) Is not correct
b) Is not correct
c) Is correct
d) Is not correct

Explanation / Rationale

“Small garden” and “large garden” can go only with “ground floor”, so we need two test cases with “ground floor” which cover these two “garden type” partitions.
We need two more test cases to cover the two other “floor” partitions and a remaining ”garden type” partition of “no garden”.
We need a total of four test cases:

TC1 (ground floor, small garden)
TC2 (ground floor, large garden)
TC3 (first floor, no garden)
TC4 (second or higher floor, no garden)

Thus:
a) Is not correct
b) Is correct
c) Is not correct
d) Is not correct