[ISTQB-TA]Chap 3.3

Defect-Based Techniques

  - is one in which the type of defect sought is used as the basis for test design, with tests derived systematically from what is known about the type of defect.

  - derives tests from defect taxonomies

  - The taxonomies can include lists of defect types, root causes, failure symptoms, and other defect-related data.

  - may also use lists of identified risks and risk scenarios as a basis for targeted testing.

 

 

Applicability

  - can be applied at any testing level but is most commonly applied during system testing.

  - there may not be any taxonomies available for innovative software.

 

Coverage

  - provides coverage criteria that are used to determine when all the useful test cases have been identified.

  - the coverage criteria for defect-based techniques tend to be less systematic than for specification-based techniques in that only general rules for coverage are given and the specific decision about what constitutes the limit of useful coverage is discretionary.

 

Types of Defects

  - The types of defects discovered usually depend on the taxonomy in use.

  - If a user interface taxonomy is used, the majority of the discovered defects would likely be user interface related, 

but other defects can be discovered as a byproduct of the specific testing.

 

Defect Taxonomies

  - can be very general and used to serve as high-level guidelines or can be very specific.

  - Detailed taxonomies can be redundant, but they allow a test team to divide up the testing 

without a loss of information or coverage.

 

 

Experience-Based Techniques

  - When using dynamic and heuristic approaches, testers normally use experience-based tests, and testing is more reactive to events than pre-planned testing approaches.

  - execution and evaluation are concurrent tasks.

  - Some structured approaches to experience-based tests are not entirely dynamic, 

i.e., the tests are not created entirely at the same time as the tester executes the test.

 

1) Error Guessing

  - error guessing is also useful during risk analysis to identify potential failure modes.

 

Applicability

  - is done primarily during integration and system testing, but can be used at any level of testing.

  - is often used with other techniques and helps to broaden the scope of the existing test cases.

  - Checklists and taxonomies may be helpful in guiding the testing.

 

 

Limitations/Difficulties

  - Coverage is difficult to assess and varies widely with the capability and experience of the Test Analyst.

  - is frequently not documented and so maybe less reproducible than other forms of testing.

 

Coverage

  - When a taxonomy is used, coverage is determined by the appropriate data faults and types of defects. 

Without a taxonomy, coverage is limited by the experience and knowledge of the tester and the time available.

 

Types of Defects

  - Typical defects are usually those defined in the particular taxonomy or “guessed” by the Test Analyst, 

that might not have been found in specification-based testing.

 

2) Checklist-Based Testing

  - Because checklists are high-level and tend to lack the detailed steps commonly found in test cases and test procedures, the knowledge of the tester is used to fill in the gaps.

  - By removing the detailed steps, checklists are low maintenance and can be applied to multiple similar releases.

  - Checklists can be used for any level of testing.

  - Checklists are also used for regression testing and smoke testing.

 

Limitations/Difficulties

  - The high-level nature of the checklists can affect the reproducibility of test results.

  - It is possible that several testers will interpret the checklists differently and will follow different approaches to fulfill the checklist items. This may cause different results, even though the same checklist is used.

  - This can result in wider coverage but reproducibility is sometimes sacrificed.

  - can be derived from more detailed test cases or lists and tend to grow over time.

  - Maintenance is required to ensure that the checklists are covering the important 

aspects of the software being tested.

 

 

Coverage

  - The coverage is as good as the checklist but, because of the high-level nature of the checklist, 

the results will vary based on the Test Analyst who executes the checklist.

 

Types of Defects

  - Typical defects found with this technique include failures resulting from varying the data, 

the sequence of steps or the general workflow during testing.

 

 

 

2) Exploratory Testing

  - Exploratory testing is characterized by the tester simultaneously learning about the product and its defects, 

planning the testing work to be done, designing and executing the tests, and reporting the results.

  - The tester dynamically adjusts test goals during execution and prepares only lightweight documentation.

 

Applicability

  - Good exploratory testing is planned, interactive, and creative.

  - Exploratory testing is often used to augment other testing and to serve as a basis 

for the development of additional test cases.

 

Limitations/Difficulties

  - difficult to manage and schedule. Coverage can be sporadic and reproducibility is difficult.

  - To manage exploratory testing. Using charters to designate the areas to be covered in a testing session and time-boxing to determine the time allowed for the testing is one method used to manage exploratory testing.

  - difficult to accurately track them in a test management system.

  - This is sometimes done by creating test cases that are actually exploratory sessions. 

This allows the time allocated for the exploratory testing and the planned coverage to be tracked with the other testing efforts.

  - reproducibility may be difficult with exploratory testing. Some organizations use the capture/playback capability of a test automation tool to record the steps taken by an exploratory tester.

  

Coverage

  - Charters may be created to specify tasks, objectives, and deliverables.

  - Exploratory sessions are then planned to achieve those objectives.

 

Types of Defects

  - Typical defects found with exploratory testing are scenario-based issues that were missed during scripted functional testing.

  - issues that fall between functional boundaries, and workflow-related issues.

  - Performance and security issues are also sometimes uncovered during exploratory testing.

 

 

 

 

They(Defect- and experience-based techniques) range from “quick tests” in which the tester has no

formally pre-planned activities to perform, through pre-planned sessions to scripted sessions.

 

They are almost always useful but have particular value in the following circumstances

  No specifications are available 

  There is poor documentation of the system under test 

  Insufficient time is allowed to design and create detailed tests 

  Testers are experienced in the domain and/or the technology 

  Diversity from scripted testing is a goal to maximize test coverage 

  Operational failures are to be analyzed