CTFL-Foundation Sample Questions Answers

Equivalence Partitioning is a black-box testing technique that divides the input data of a software unit into partitions of equivalent data from which test cases can be derived. It helps in reducing the number of test cases while maintaining adequate test coverage.

The value of static code analysis lies in its ability to detect defects early in the development process. By analyzing the code without executing it, static analysis can identify potential issues, such as coding errors or violations of coding standards, which can be addressed before they lead to more significant problems.

Effective ways to improve communication and relationships between testers and other team members include communicating factual information in a constructive way (a) and trying to understand how the other person feels and why they react the way they do (b). These approaches foster a collaborative and empathetic environment, reducing friction and enhancing teamwork.

Exit criteria are the conditions that must be met to conclude a particular phase of testing. These criteria include acceptance criteria, completion criteria, and pass/fail criteria. They help ensure that the testing process is thorough and that the system meets the required standards before moving on to the next phase.

Static analysis is a technique used to find defects in software source code and software models without executing the code. It involves reviewing the code or models to identify potential issues, such as syntax errors, logical errors, or security vulnerabilities. Static analysis helps improve code quality and maintainability by catching defects early in the development process​​.

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Testing support tools are typically used to automate activities that are resource-intensive when done manually, repetitive tasks, and repetitive inspections. However, they are not usually designed to automate activities that cannot be executed manually at all, as such activities may require complex and sophisticated human intervention or decision-making.

The requirements for reliability and security in a product significantly impact the testing effort. High requirements for reliability and security necessitate more extensive and thorough testing to ensure that the product meets these stringent criteria. This often includes additional test cases, more complex test environments, and longer test execution times.

Common metrics used for monitoring test preparation and execution typically include quantitative measures such as the number of test cases passed and failed, the percentage of planned test cases designed, and the percentage of tasks completed in test environment preparation. These metrics provide insights into the progress and effectiveness of the testing process. However, the number of test plan review comments is not a typical metric for this purpose, as it does not directly measure the progress or quality of test execution​​.

Static analysis tools are designed to analyze code without executing it. They are particularly good at finding defects related to code structure, such as variables that are not used or improperly declared. These tools can parse the code and identify issues that may not be easily detected through dynamic testing methods. Other issues like omission of a major requirement (A), inadequate decision coverage (B), and component memory leakage (C) are typically found through dynamic testing or higher-level verification techniques​​ .

Providing support for the test team using the tool is crucial for successful deployment. This includes training the test team on how to effectively use the tool, offering ongoing support to address any issues, and integrating the tool into existing processes. By ensuring that the team is well-equipped and confident in using the tool, the organization can maximize the benefits of the tool and improve overall testing efficiency​​.

Equivalence Partitioning is a black box test design technique used to divide input data into partitions that are expected to be treated the same by the system. It focuses on ensuring that each partition represents a set of valid or invalid states for the input, and one test case from each partition is enough to cover the entire set. This technique does not rely on the internal structure of the code but rather on the functionality and behavior as seen from the user's perspective​​.

Debugging is the process that involves locating the cause of a failure and fixing the defect. Therefore, activities b) "Locating the cause of failure" and c) "Fixing the defect" are debugging activities. Identifying a failure and checking that the fix has resolved the failure are parts of testing, not debugging​​.

Maintenance testing is typically triggered by changes to the operational system, such as data migration, system modification, or system retirement. These triggers require testing to ensure that the changes do not negatively impact the existing functionality. However, the introduction of a test management tool does not directly affect the operational system and is not considered a trigger for maintenance testing​​.

During the test planning stage, it is important to assign resources for the planned activities. This ensures that the necessary personnel, equipment, and time are allocated to execute the test plan effectively. Analyzing the test basis, designing test environments, and writing a test execution schedule are activities that come after the initial planning and resource allocation​​.

The correct logical order for the test cases ensures a smooth and realistic flow through the system functionalities. The sequence should start with logging into the system (Test Case 3), searching for available flights (Test Case 1), selecting an available flight (Test Case 4), viewing the selected item in My Flights (Test Case 2), confirming details and booking the flight in My Flights (Test Case 6), and finally printing the confirmation receipt and exiting (Test Case 5)​​ .

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The correct sequence in the causal chain is "Error, fault, failure". An error (or mistake) made by a person can lead to a fault (or defect) in the software. When the fault is executed, it may cause a failure in the software system. This sequence is important to understand the cause and effect relationship in software testing and defect management​​ .

The level of risk is determined by evaluating both the impact and the likelihood of an adverse event occurring. This approach ensures that both the severity of potential consequences and the probability of the event are considered. The impact assesses how serious the consequences would be if the event happened, while the likelihood evaluates how probable it is that the event will occur. This combination provides a comprehensive measure of risk, helping organizations prioritize their risk management efforts effectively​​.

Exploratory testing is highly effective when under severe time pressure because it allows testers to simultaneously learn, design, and execute tests. It is a flexible approach that does not require extensive preparation and documentation, making it ideal for situations where time is limited​​.

The amount of testing effort is highly influenced by the predicted number of defects and the subsequent amount of rework required. If a high number of defects are expected, more effort will be needed to identify, document, and retest the defects after they are fixed. This impacts the overall testing workload significantly compared to other factors such as the ratio of developers to testers, which affects team dynamics but not the core testing effort​​.

Functional and structural testing can be applied at all test levels. Functional testing focuses on verifying that the software behaves as expected based on the requirements, while structural testing examines the internal structure and workings of the software. These testing approaches are complementary and can be used together at various stages of testing, including component, integration, system, and acceptance testing. Applying both types of tests ensures a comprehensive evaluation of the software's functionality and internal structure​​.

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Load testing is a type of non-functional testing used to verify that the system can handle a specified load of users performing transactions within acceptable performance parameters. In this case, load testing would ensure that up to 100 users can carry out transactions simultaneously with response times within 5 seconds. This testing helps identify performance bottlenecks and ensure that the system meets the performance requirements under expected user load conditions​​.

A keyword-driven testing approach is effective because it separates the test logic (actions) from the test data. This makes the scripts more reusable and easier to maintain. By organizing tests this way, any changes in the data or the actions can be made independently without affecting the other, enhancing the efficiency and manageability of automated tests​​.

According to the decision table, Test Case 1 is valid because an employee who is not a car or motorcycle driver cannot claim expenses, as shown in Rule 1. Test Case 3 is valid because a motorcycle driver can claim expenses, as indicated in Rule 2, with expenses claim band A. However, Test Case 2 is invalid because, according to Rule 5, a car driver with a diesel engine greater than 1600cc cannot claim expenses. The expected result should be that the expense claim is not allowed, not band C​​.

Writing test summary reports is typically the responsibility of a test leader or manager, who consolidates testing activities and results to communicate with stakeholders. Testers are more involved in preparing and acquiring test data, setting up and checking the test environment, and reviewing tests developed by others. These tasks are more hands-on and technical, aligning with the role of a tester​​ .

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Measurement of code coverage is important because it helps ensure that all code is exercised by tests. This does not guarantee that there are no coding errors or that all requirements are covered, but it helps identify untested parts of the code, allowing for better test coverage and more robust testing processes​​.

According to the decision table:

For TC1, since Paul is not a full member but is a Loyalty Card holder and requests 18 holes with a buggy/cart, the applicable action is £18 Green Fees plus £5 for buggy/cart, totaling £23.

For TC2, since Cheryl is not a full member, does not have a Loyalty Card, and requests 9 holes with a buggy/cart, the applicable action is £16 Green Fees with no buggy allowed​​.

Testing is primarily aimed at detecting defects, verifying the functionality, and providing information to stakeholders for decision-making. While investigating defects is part of the testing process, fixing defects is not typically considered an objective of testing; it falls under the development activities. The main objectives of testing include preventing defects (through early testing activities), gaining confidence in the system, and providing valuable information to stakeholders​​.

Static analysis tools are designed to analyze code without executing it. They are highly effective at identifying issues such as syntax errors, variable declaration, and usage problems. Options A, B, and D are types of defects that static analysis tools can typically detect because they relate to the code structure and syntax. However, Option C refers to a variable having the wrong numeric value passed into it, which is more of a logical error that typically requires dynamic testing to identify. Static analysis tools cannot understand the correct logical flow or expected values in the code, thus making Option C the correct answer​​ .

The pesticide paradox in testing refers to the phenomenon where continuously using the same set of tests on the software eventually becomes less effective at finding new defects. Just as insects can develop resistance to pesticides over time, software defects become less detectable by tests that are not updated. Therefore, to maintain the effectiveness of testing, it is essential to regularly review and revise the test cases to introduce new tests and update existing ones​​.

Decision coverage is a testing metric used to ensure that all possible paths (decisions) in the code have been executed at least once. It is not used to verify the correctness of module calls, which ismore related to integration testing or control flow testing. Options A, B, and D describe valid uses of decision coverage, ensuring that decisions are exercised in programs, business processes, and measuring the extent of coverage by a test suite​​ .

A dynamic analysis tool would have been the most effective at detecting a defect where a code component fails to release memory after use. These tools analyze the behavior of the software while it is running, allowing them to identify issues like memory leaks, which occur when memory is not properly freed. Dynamic analysis tools can monitor the allocation and deallocation of memory in real-time, helping to pinpoint the exact location and cause of the memory leak before the software is deployed​​ .

The highest level of testing independence is achieved when the testing process is performed by individuals or teams who are completely independent of the development team and the organization. Option B, which involves outsourcing test design and execution to a different company, ensures that there is no bias or influence from the development team or company politics, thereby achieving the highest level of testing independence​​.

Equivalence partitioning is a black-box test design technique that divides input data into partitions that are expected to be treated similarly by the system. In this case, 0600 falls into the peak-time tariff, 1000 is at the boundary of peak-time but still included in it, and 1200 falls into the off-peak tariff. This ensures that each input is from a different equivalence partition, testing different functional areas of the system​​.

To meet the test plan requirements and logical dependencies, the test schedule should start with re-tests (those that have previously failed), followed by the highest priority tests. Additionally, tests should be scheduled to create necessary test data for subsequent tests. In this case, teste(log in as admin user and create a standard user) must be done first as it is necessary to perform all other actions. Following this, testa(log in as standard user and create customer account) creates the standard user needed for subsequent actions. Then, the highest priority testd(order twoitems or more), which has failed before, should be executed next, followed by testc(create invoice for order), and finally testb(order one item)​​.

Test execution tools include tools that directly assist in the execution of tests and comparison of actual outcomes with predicted outcomes. A test harness (b) is used to execute tests by providing the necessary context and data inputs for running a test. Test comparators (d) are used to compare the actual results produced by the system under test with the expected results, which is a key part of test execution.

Typically, exit criteria may consist of various metrics that indicate whether testing has been sufficiently thorough. Estimates of defect density or reliability measures are common exit criteria used to decide if the software is ready for the next stage or release. These criteria help in assessing the quality and stability of the software based on the number and severity of defects found during testing​​.

Statement coverage is a white-box testing technique that involves executing all the statements in the code at least once. It is not considered a black-box technique because it requires knowledge of the internal structure of the code being tested. Black-box techniques, such as equivalence partitioning, state transition testing, and boundary value analysis, focus on testing the functionality of the software without considering its internal code structure.

According to the IEEE 829 Standard for Software Test Documentation, an incident report should include the identification of configuration items of the software or system (i), the software or system lifecycle process in which the incident was observed (ii), a description of the anomaly to enable reproduction of the incident (iii), and the classification of the cause of the incident formetrics and reporting purposes (v). The number of occurrences of the incident is not typically included.

For a review process to be successful, several factors must be in place. According to the ISTQB syllabus, successful reviews generally have clearly defined objectives (a), involve the right people who understand the objectives of the review (c), and place an emphasis on learning and process improvement (d). These elements ensure that the review is focused, effective, and contributes to the overall improvement of the software development process​​.

The appropriate test execution schedule considering the prioritization and constraints should start with re-tests, followed by the regression test script. After these, tests should be run based on their priority levels:

a (Re-test defect no 52, Low priority, Re-test)

c (Re-test defect no 26, High priority, Re-test)

d (Run regression test script, Medium priority, Regression)

b (Ability to amend transaction type, High priority)

g (Reprint selected previous sales figures, High priority, Must be run after item e)

e (Print monthly sales figures, Medium priority)

i (Print year-to-date figures, Medium priority)

f (Add special invoice to previous month, Low priority)

h (Account administrator able to amend any previous month’s sales figures, Low priority)

This sequence ensures that re-tests and high-priority tasks are completed first, followed by medium-priority tasks, and then low-priority tasks.

Based on the given flow graph and the test cases provided:

Test Case 1 covers the path P → Q → R → U.

Test Case 2 covers the path P → Q → S → V.

Test Case 3 covers the path P → Q → S → W → X.

Test Case 4 covers the path P → Q → S → W → Y.

All decision points (P, Q, R, S, W) are covered at least once, ensuring 100% decision coverage. However, not all statements (T) are covered, as there is no test case that covers the path leading to statement T.

One of the considerations when deploying test execution tools is that recorded manual tests may become unstable. This instability can be due to changes in the user interface, environment, or other dependencies that the recorded script relies on. As a result, maintaining these recorded tests can be challenging and may require frequent updates.

A test condition is defined as an item or event that can be verified by one or more test cases. It can include functions, transactions, structural elements, or quality attributes that need to be tested to ensure the system behaves as expected.

The failure rate in testing already completed is a useful metric to monitor progress along with test preparation and execution. It provides insight into the effectiveness of the tests and the quality of the product, helping to identify areas that may require additional attention or resources.

One limitation of static analysis tools is that they tend to generate a large number of warning messages when applied to new code. This can occur even if the code meets established coding standards, as the tools are designed to identify a wide range of potential issues, leading to a high volume of output that needs to be reviewed and addressed.

The application failed due to a defect in the purchase identification module. This defect could have been caused by a programmer mistake or an error in the specification. The incorrect counting of purchase attempts indicates a flaw in the logic or implementation of the module responsible for identifying successful purchases.

For a safety-critical system, it is essential to ensure that regression tests are run and passed following defect corrections at all test levels. Additionally, tracking incidents raised and closed at all levels of testing helps ensure that all defects are addressed and the system meets safety standards. These metrics provide a comprehensive view of both the completeness of testing and the effectiveness of defect resolution.

In formal reviews, such as inspections, the role of the moderator is crucial. The moderator is responsible for leading the review process, ensuring that the review is conducted according to the defined procedures, and facilitating the review meeting. The ISTQB syllabus highlights that the moderator's role is to guide the review team, manage any issues that arise during the review, and ensure that the objectives of the review are met​​.

Determining whether enough testing has been performed involves considering several factors. These include:

(i) The exit criteria, which define the conditions that must be met to conclude testing. (ii) The budget, which affects the extent of testing that can be conducted. (iv) The product's risk profile,which helps prioritize testing efforts on high-risk areas. (vi) Sufficient details of the system status to allow decisions, ensuring that stakeholders have the necessary information to make informed decisions about the software's readiness.

These factors together ensure a balanced and informed decision-making process regarding the sufficiency of testing​​.

Independence in software testing refers to the separation of testing activities from the development and production processes. This separation helps ensure objectivity and reduces the risk of bias in the testing results. Independent testers are more likely to identify defects that developers might overlook due to familiarity with the code. The ISTQB syllabus highlights the importance of independence in testing as a key factor in promoting effective and unbiased testing practices​​.

A data-driven approach to test automation design involves separating the test data inputs from the test scripts. This approach allows the same generic script to read different sets of test data and execute the same test steps with various inputs. This method enhances reusability and efficiency in automated testing by allowing testers to run multiple test scenarios using the same script but different data sets​​.

The selection of test cases for regression testing requires a comprehensive approach. It involves:

A. Knowledge on the bug fixes and how they affect the system to ensure that new changes do not reintroduce old defects.

B. Includes the area of frequent defects to prioritize testing on parts of the software that have a history of issues, thus ensuring that known problem areas are thoroughly tested.

C. Includes the area which has undergone many/recent code changes to verify that new changes have not adversely affected existing functionality.

Combining all these aspects ensures a robust regression testing process, which minimizes the risk of defects in the software after changes are made​​.

Designing the tests is part of the Test Analysis and Design phase, not the Test Implementation and Execution phase. The Test Implementation and Execution phase involves creating test suites, executing test cases, and comparing actual results with expected outcomes to identify any discrepancies​​.

Variance from programming standards defects (option (A)) are found during the review or static testing process. Therefore a test harness is unlikely to find a defect in programming standards.

Memory leak defects (option (C)) could potentially be found by a test harness designed to run many test cases.

Regression defects (option (D)) could be found using many types of test tool.

Defects in middleware (option (B)) are generally more likely to be found by a test harness or a dynamic analysis tool than by any other type of tool.

One of the primary objectives of software testing is to uncover software errors. The ISTQB CTFL syllabus v4.0 emphasizes that testing aims to find defects, verify that the software works as expected, and ensure that it meets the specified requirements. Other objectives include preventing defects, evaluating the quality of the software, and providing information to stakeholders​​.

A tool that supports traceability, recording of incidents, or scheduling of tests is called a test management tool. These tools help in planning, managing, and tracking the testing process, providing features for managing test cases, tracking defects, and maintaining traceability between test artifacts​​.

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Test independence is beneficial because it helps to avoid author bias, ensuring that the tests are designed and executed objectively. When testers who are not involved in the development of the code test it, they bring a fresh perspective and are more likely to identify defects that the developers might have overlooked due to familiarity with their own work. This principle is supported by the ISTQB CTFL Syllabus, which highlights that independence can enhance the effectiveness of testing by eliminating the preconceived notions and biases of those who wrote the code​​.

The Author is the only role that is typically used in a review.

A Champion might sponsor the review process but is not a defined role within an actual review; a Project Sponsor, if technically competent, might be asked to play a defined role within the review process, but whilst using that role they will not be a Project Sponsor; finally, a Custodian might ensure the results are stored safely but would not be involved in the actual review itself.

Reviewing the test basis is a key activity in the Test Analysis and Design phase. This phase involves analyzing the test basis documents (such as requirements, design specifications, and use cases) to identify test conditions and design test cases. The ISTQB CTFL Syllabus explains that thorough review of the test basis ensures that the tests are aligned with the specified requirements and design, improving the accuracy and relevance of the tests​​.

Non-functional requirements define how the system performs a certain function, rather than specific behaviors or functions of the system. Security, performance, usability, reliability, and maintainability are common examples of non-functional requirements. Ensuring the security of customer details is a non-functional requirement because it specifies a quality attribute that the system must have. Reference: ISTQB CTFL Syllabus V4.0, Section 4.1​​.

The purpose of exit criteria is to determine when to stop testing. Exit criteria are specific conditions or set of conditions agreed upon to declare that a particular test level or a test activity is completed. These criteria are used to ensure that the testing process has reached a certain level of coverage and quality before it is considered complete. Typical exit criteria include achieving a certain level of code coverage, passing a specified number of tests, or fixing a certain number of defects. Reference: ISTQB CTFL Syllabus V4.0, Section 5.1.3 .

Incidents, or defects, are typically raised against artifacts such as requirements, documentation, and test cases when they do not meet their expected outcomes or contain errors. However, improvements suggested by users are not considered incidents, as they are enhancements or changes that users would like to see, rather than defects in the current functionality or documentation.

The handover of testware occurs during the Test Closure Activities phase. This phase includes collecting data from completed test activities to consolidate the experience, testware, and any other relevant information for future use. Testware handover involves delivering all test artifacts such as test cases, scripts, and test data to maintenance teams, ensuring that valuable test assets are not lost and can be reused or referenced in future maintenance or development cycles​​.

The V-model enables test planning to start as early as possible. This model is an extension of the waterfall model and emphasizes the importance of early test planning and development of test cases, which corresponds to the development stages. By planning tests early, the V-model ensures that testing is integrated into every phase of the software development lifecycle. Reference: ISTQB CTFL Syllabus V4.0, Section 2.1.2​​.

Debugging is the process that developers follow to find, analyze, and fix the root causes of defects in the software. This includes identifying the source of the problem, correcting the code, and then testing the changes to ensure the defect has been properly fixed and that the fix does not introduce new issues.

It is unlikely that developers will have a better understanding of the requirements than testers, partly because testers work closely with the user community (and may be drawn from it) and partly because developers seldom work with the complete set of requirements in a medium to large development.

Testers may raise incidents related to the difference between user expectations and the specification, but these are not unnecessary. Such issues are more likely to arise at the later stages of testing.

Early testing (unit testing) is usually done most effectively by developers with a good understanding of the code and the development environment; they can be more efficient andmore effective at this level. Later independent stages of testing offset any disadvantage from the lack of independence at unit testing level.

The concept of introducing a small change to the program and having the effects of that change show up in some test is known as "introducing mutations." This is part of mutation testing, where small changes (mutations) are made to the code to see if the existing test cases can detect the errors introduced by these changes. The goal is to evaluate the effectiveness of the test cases in identifying defects. Reference: ISTQB CTFL Syllabus V4.0, Section 4.3.4​​.

Non-functional system testing evaluates various quality attributes of a system rather than specific behaviors or functionalities. According to the ISTQB CTFL Syllabus, version 4.0, non-functional testing encompasses several critical aspects:

Performance testingevaluates how the system performs under different conditions, such as load and stress, to ensure it meets performance requirements.

Usability testingassesses the user-friendliness and overall user experience of the system, ensuring that it is intuitive and accessible for end-users.

The syllabus outlines that non-functional system testing includes testing the quality attributes of the system, which goes beyond just functionality and delves into performance, usability, reliability, and other key attributes​​.

A defect, also known as a bug, is a flaw in a component or system that can cause it to fail to perform its required function. Defects arise from errors made by people, such as mistakes in code or design. When a defect in the software is executed, it can cause the system to behave unexpectedly, leading to failures. The relationship between errors, defects, and failures is crucial to understanding the importance of early detection and correction in the software development lifecycle.

Developers often have difficulty testing their own work primarily due to a lack of objectivity. When developers test their own code, they might unconsciously overlook errors because they are too familiar with the code and its intended functionality. This lack of impartiality can lead to missed defects and a biased view of the code's quality. Independent testing by other testers or teams helps to mitigate this issue by providing an objective perspective​​.

Code Coverage is a measure used to describe the degree to which the source code of a program is tested by a particular test suite. It helps in determining the effectiveness of testing by indicating the parts of the code that have been exercised by the tests and those that have not. It is an important metric for evaluating test coverage and identifying areas that may require additional testing. Reference: ISTQB CTFL Syllabus V4.0, Section 4.3.2​​.

The typical sequence of formal review activities includes planning, kick-off, individual preparation, and review meeting. The planning phase sets the scope and objectives, the kick-off initiates the review process, individual preparation involves participants reviewing the materials on their own, and then the review meeting is held to discuss the findings. Reference: ISTQB CTFL Syllabus V4.0, Section 3.2.2​​.

Re-testing and regression testing are essential concepts in software testing, each serving a different purpose. According to the ISTQB CTFL Syllabus, version 4.0, the difference between these two types of testing is highlighted as follows:

Re-testing(also known as confirmation testing) involves executing the same tests again on the same version of the software after defects have been fixed. The primary goal is to confirm that the original defects have been successfully removed and that the software behaves as expected.

Regression testing, on the other hand, is performed to ensure that recent code changes have not adversely affected the existing functionalities of the software. This testing aims to detect any unexpected side effects introduced by the new changes.

The syllabus states: "Re-testing is running a test again; regression testing looks for unexpected side effects"​​. This explanation clarifies that while re-testing focuses on verifying specific defect fixes, regression testing ensures the overall stability and integrity of the software after changes.

Static analysis of a software model is most likely to be performed by developers. This involves examining the code and software structure without executing the program, using tools to identify potential issues, such as coding standards violations, security vulnerabilities, and other quality issues. Developers often use static analysis as part of their development process to ensure code quality and maintainability. Reference: ISTQB CTFL Syllabus V4.0, Section 3.1.1​​.

Requirements management tools (ii) have traceability because they enable test conditions and subsequently test scripts and defects to be traced back to requirements. Configuration management tools (iii) also need to trace the appropriate version of a test script to the release or version of a system or module.

Performance monitoring tools (i) and static analysis tools (iv) are designed for specific objectives. Neither of these tools particularly need traceability functions.

Boundary value analysis focuses on the values at the edges of equivalence partitions. For an input range of 1900 to 2004, the boundary values are just inside and just outside the range:

Just inside: 1900, 2004

Just outside: 1899, 2005

Therefore, the boundary values are 1899, 1900, 2004, and 2005. Reference: ISTQB CTFL Syllabus V4.0, Section 4.2.1​​.

In the MASPAR case study, several key issues were highlighted. Security failures were attributed to untested parts of code (A), despite achieving complete statement and branch coverage, a serious bug was still missed in the MASPAR operating system (B). Additionally, an obscure error required testing the function with nearly every input value to find the two special-case failures (C). Therefore, all thesepoints together (D) illustrate the complexity and challenges in software testing. Reference: ISTQB CTFL Syllabus V4.0​​.