Test Types – D, E, F

Test Type
A particular type of testing that has an approach, goal and/or use of oracle(s) that provides information that is typical to that test type.

This is the third post in a (sub) series on Test Types. This post covers test types beginning with D, E and F. Please add any additions or remarks in the comment section.

Data integrity testing
Data integrity testing focusses on the verification and validation that the data within an application and its databases remains accurate, consistent and retained during its lifecycle while it is processed (CRUD), retrieved and stored.
I fear this is an area of testing that is often overlooked. While it gets some attention when functionality is tested initially, the attention on the behavior of data drops over time.

Dependency testing
Examines an application’s requirements for pre-existing software, initial states and configuration in order to maintain proper functionality.

Destructive testing
Test to determine the softwares or its individual components or features point of failure when put under stress.
This seems very similar to Load Testing but I like the emphasis on individual stress points.

Development testing
It is an existing term with its own Wikipedia page but it doesn’t bring anything useful to software testing as such.

Documentation testing
Testing of documented information, definitions, requirements, procedures, results, logging, test cases, etc.

Dynamic testing
Testing the dynamic behavior of the software.
Almost all testing falls under this definition. So in practice a more specific identification of a test type should be chosen.

End-to-End testing
Testing the workflow of a single system or a chain of systems with regard to its inputs, outputs and processing  of these with regard to its availability, capacity, compatibility, connectivity,  continuity, interoperability, modularity, performance, reliability, robustness, scalability, security, supportability and traceability.
While in theory end-to-end testing seems simple. Enter some data and check that it is processed and handed over throughout all systems until the end of the chain. In practice end-to-end testing is very difficult. The long list of quality characteristics mentioned above serves as an indication of what could go wrong along the way.

Endurance testing
Endurance is testing the ability to handle continuous load under normal conditions and under difficult/unpleasant conditions over some longer period of duration/time.

Error handling testing
Use specific input or behavior to generate known, and possibly unknown, errors.
Documented error and of exception handling is a great source to use for test investigations. It shows often undocumented requirements and business logic. It also interesting to see if the exception and errors occur based upon the described situation.

Error guessing
Error guessing is based on the idea that experienced, intuitive or skillful tester are able to find bugs based on their abilities and that it can be used next the use of more formal techniques.
As such one could argue that it is not as much a test type as it is an approach to testing. 

Exploratory testing
Exploratory testing is a way of learning about and investigating a system through concurrent design, execution, evaluating, re-design and reporting of tests with the aim to find answers to currently known and currently as yet unknown question who’s answers enable individual stakeholders to take decisions about the system.
Exploratory testing is an inherently structural approach to testing that seeks to go beyond the obvious requirements and uses heuristics and oracles to determine test coverage areas and test ideas and to determine the (relative) value of test results. Exploratory testing is often executed on the basis of Session Based Test Management using charter based and time limited sessions.
It is noteworthy that, in theory at least, all of the test types mentioned in this series could be part of exploratory testing if deemed appropriate to use. 

Failover testing
Failover testing investigates the systems ability to successfully failover, recover or re-allocate resources from hardware, software or network malfunction such that no data is lost, data integrity is intact and no ongoing transactions fail.

Fault injection testing
Fault injection testing is a method in which hardware faults, compile time faults or runtime faults are ‘injected’ into the system to validate its robustness.

Functional testing
Functional testing is testing aimed to verify that the system functions according to its requirements.
There are many definitions of functional testing and the one above seems to capture most. Interestingly some definitions hint that testing should also aim at covering boundaries and failure paths even if not specifically mentioned in the requirements. Other mention design specifications, or written specifications. For me functional testing initially is conform the published requirements and than to investigate in which way this conformity could be broken. 

Fuzz testing
Fuzz testing or fuzzing is a software testing technique, often automated or semi-automated, that involves providing invalid, unexpected, or random data to the inputs of a computer program. The program is then monitored for exceptions such as crashes, or failing built-in code assertions or for finding potential memory leaks.
Yes this is more or less the Wikipedia definition. 

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Test Types – A

This sixth post in the series of software testing overviews introduces the first of some 80+ different test types. That number itself is completely arbitrary. While searching for and investigating testing definitions I found over a hundred definitions of test types and I have chosen to leave out a number of ‘test types’. My choice to do so is based on the interpretation that some test types rather described a test level or a test technique and I could not see how to make a useful test type out of them.

So what then do I call a test type?

To me a test type is a particular subject of testing that has an approach, goal and/or use of oracle(s) that provides information that is typical to that test type.

While going through my overview you might find that some of the test types I mention do not entirely fit the narrow description of a test type as provided above. The reason that they are mentioned in spite of this is that I felt that they were so often mentioned as a test type that they should have a mention in this post just for that reason.

This post differs somewhat from the earlier posts as the definitions used are often rewritten by me to form a single aggregate definiton as many different ones for the same term exist. Where useful I have added comments as additional information. Also since a post with over 80 descriptions would be too long I have split up the overview into alphabetical sections. To begin with the letter A.

Just as a reminder these are not necessarily my definitions but a collection of definitions I encountered. Finally there are no sources or attributions for the individual test types as this would make this a totally different exercise.

A/B testing

A/B testing originates from marketing research used to investigate the more efficient of two possible solutions by presenting them to two different groups and measuring the ‘profits’. In software testing it is mostly used to compare two versions of a program or website, often of which only one contains changes on a single or a few controllable criteria.

Acceptance testing
During acceptance testing requirements, variables, parts of a program or specific behaviour of a program is compared against measurable aspects of predetermined acceptance criteria. This requires at least four things.
First identification of the requirements, variables and parts or behaviour (coverage). Second expressing these in measurable aspects.
Third the aspects need to represent the defining elements of the acceptance criteria. Finally the acceptance criteria themselves should represent the needs and wants of the stakeholder. The goal of this interpretation of acceptance testing is to provide stakeholders the possibility to accept the software. And provide the possibility of sign-of.

A more pragmatic way to look at acceptance testing is to allow the stakeholders, often end users, to evaluate the software and see if it meets there expectations and (operational) needs. In practice this is often done by proxy by stakeholder representatives. Sometimes the testers are selected as the representatives. I do not think that is a good idea as testers then step outside of there boundary of information provider, are often commited to the solution and their role in creating it and more essentially testers are not the end users. 

Active testing
Testing the program by triggering actions and events in the program and studying the results. To be honest I do not consider this a test type as in my opinion this describes nearly all types of testing.

Ad-hoc testing

Ad-hoc testing is software testing performed without explicit prior planning or documentation on direction of the test, on how to test or on which oracles to use.
Some definitions see this as informal, unstructured and not reproducible. Informality and being unstructured (if seen as unprepared) is certainly true as this would be the point of doing it ad-hoc. The not reproducible part depends on whether you care to record the test progress and test results. Something that is in my opinion is not inherently attached to doing something ad-hoc but highly advisable. Why elso would you be testing if you are able to tell the testing story.

Age testing
It is a testing technique that evaluates a system’s ability to perform in the future. As the system gets older, how significantly the performance might drop is what is being measured in Age Testing.
To be honest I found only one reference to this test type but I find the idea interesting. 

Agile testing
Agile testing is mentioned often as a test type or test approach but I have added no definition or description here. In my opinion agile testing is not a software test type. Agile testing rather is a particular context in which testing is performed that may have its particular challenges on test execution, on how tests are approached and on choices of test tooling but not a specific test type. 

Alpha testing
Alpha testing is an in-house (full) integration test of the near complete product that is executed by others than the development team but still is executed in a development environment. Alpha testing simulates the products intended use and helps catch design flaws and operational bugs.
One could argue that this is more of a test level than a test type. I care to view it as test type because it is more about the type of use and its potential to discover new information than that it is part of the software development itself. I specifically disagree with the idea that this is an intermediary step towards, or is part of, handing over software to a Test/QA group as some definitions propose. In my opinion testing is integrated right from the start of development up until it stops because the product ends its life-cycle or due to some other stopping heuristic. 

API testing
API testing involves testing individual or combined inputs, outputs and business rules of the API under investigation.
Essentially an API is a device-independent, or component-independent access provider that receives, interprets/transforms and sends messages so that different parts of a computer or programs can use each other’s operations and/or information. Testing an API is similar to testing in general albeit that an API has a smaller scope has, or should have, specific contracts and definitions that describe the API’s specific variables, value ranges and (business) rules. Testing an API should however not be limited to the API alone. Sources, destinations (end-points), web services (e.g. REST, SOAP), message types (e.g. JSON, XML), message formats (e.g. SWIFT, FIX, EDI, CSV), transport- (e.g. HTTP(S), JMS, MQ)  and communication protocols (e.g. TCP/IP, SMTP, MQTT, TIBCO Rendezvous) all influence the overall possibilities and functionality of the API in relation to the system(s) that use(s) the API. Typically API testing is semi- or fully automated and requires sufficient tool, message type, and transport- and communication protocol knowledge to be executed well.

An alternative meaning of API testing is testing by using an API. In this case the API is a means to an end in gaining access to the subject under test and feeding it with data or instructions and gathering responses.

Regression Testing

As a follow up in the testing definition series it was my intention to continue with covering Test Types. Initial investigation showed what I had already feared. Such a post would become a Herculean task and probable my longest post ever. So I will continue with that particular endeavor sometime later tackling it one step at a time. This post for starters covers one of the most common but also one of the most peculiar types of testing

“Regression Testing”

Regression Testing is so common as a testing type that the majority of books about software testing, and agile for that matter, that I know, mention regression testing. Almost as common however is that most of them either or both do not tell what regression testing is or do not tell how one should actually go about and do regression testing. To be fair an exception to the latter is that quite a few, particularly the ones with an agile demeanor, tell that regression testing is done by having automated tests but that is hardly anymore informative is it.

Before I go further into regression testing as being peculiar first inline with the previous posts a list of regression testing definitions:

  • Checking that what has been corrected still works. (Bertrand Meyer; Seven Principles of Software Testing 2008)
  • Regression testing involves reuse of the same tests, so you can retest (with these) after change. (Cem Kaner, James Bach, Bret Pettichord; Lessons learned in Software Testing 2002)
  • Regression testing is done to make sure that a fix does what it’s supposed to do (Cem Kaner, Jack Falk, Hung Quoc Nguyen; Testing Computer Software 2006)
  • Regression testing is the probably selective retesting of an application or system that has been modified to insure that no previously working components, functions, or features fail as a result of the repairs. (John E. Bentley; Software Testing Fundamentals Concepts, Roles, and Terminology 2005)
  • Retesting to detect faults introduced by modification (ISO/IEC/IEEE 24765:2010)
  • Saving test cases and running them again after changes to other components of the program (Glenford J. Myers; The art of software testing 2nd Edition 2004)
  • Selective retesting of a system or component to verify that modifications have not caused unintended effects and that the system or component still complies with its specified requirements (ISO/IEC/IEEE 24765:2010)
  • Testing following modifications to a test item or to its operational environment, to identify whether regression failures occur (ISO/IEC/IEEE 29119-1:2013)
  • Testing if what was tested before still works (Egbert Bouman; SmarTEST 2008)
  • Testing of a previously tested program following modification to ensure that defects have not been introduced or uncovered in unchanged areas of the software, as a result of the changes made. It is performed when the software or its environment is changed. (Standard glossary of terms used in Software Testing Version 2.2, 2012)
  • Testing required to determine that a change to a system component has not adversely affected functionality, reliability or performance and has not introduced additional defects (ISO/IEC 90003:2014)
  • Tests to make sure that the change didn’t disturb anything else. Test the overall integrity of the program. (Cem Kaner, Jack Falk, Hung Quoc Nguyen; Testing Computer Software 2006)

Looking at the above definitions the general idea about regression testing seems to be:

“To ensure that except for the parts of the areas* that were intentionally changed no other parts of these areas or other areas of the software are impacted by those changes and that these still function and behave as before”.
(*Area is used here as a general expression for function, feature, component, or any other dimensional divisions of the subject under test that is used)

The peculiar thing now is that however useful and logical such a definition is it only provides the intention of this type, or should I say activity, of testing. Regression testing could still encompass any other testing type in practice.

To know what to do you first need to establish which areas are knowingly affected by the changes and then which areas have the most likelihood of being unknowingly affected by the change. Next to that there probably are areas in your software where you do not want to take the risk of them being affected by the changes. In his presentation at EuroSTAR in 2005 Peter Zimmerer addresses the consequences of this in his test design poster by pointing out that the wider you throw out your net for regression effects the larger the effort will be:

  • Parts which have been changed – 1
  • Parts which are influenced by the change – 2
  • Risky, high priority, critical parts – 3
  • Parts which are often used – 4
  • All – 5

Once you have identified the areas you want to regression test you still need to figure out how to test those areas for the potential impact of the change. The general idea to solve this, in theory at least, seems to be to rerun previous tests that cover these areas. As this might mean running numerous tests for lengthy periods of time many books and articles propose to run automated tests. This will however only work if there are automated tests to use for testing these areas to begin with. And even if there are you still need to evaluate the results of any failed test and there is no clear indication of how long that may take.

How do you know that these existing tests do test for the impact of the change? After all they were not designed to do so. For all you know they might or might not fail due to changes to the area that is tested by them. Either result could therefore be right or wrong in light of the changes. The test itself could be influenced by an impact of the change on the test (positive or negative) that was not considered or identified yet.

All in all regression testing is easily considered to be necessary, not so easy to determine, difficult to evaluate on success and considerably more work then many people think. Even so next to writing new tests it probably is the best to solution to check if changes bring about unwanted functionality or behavior in your software. My suggestion to you is to at least change the test data so that these existing tests have a better chance of finding new bugs.