Editing Sanity check

{{Short description|Test to check if a hypothesis is rational}}
A '''sanity check''' or '''sanity test''' is a basic test to quickly evaluate whether a claim or the result of a calculation can possibly be true. It is a simple check to see if the produced material is rational (that the material's creator was thinking rationally, applying [[sanity]]). The point of a sanity test is to rule out certain classes of obviously false results, not to catch every possible error. A [[rule-of-thumb]] or [[back-of-the-envelope calculation]] may be checked to perform the test. The advantage of performing an initial sanity test is that of speedily evaluating basic function.

In arithmetic, for example, when multiplying by 9, using the [[divisibility rule]] for 9 to verify that the [[digit sum|sum of digits]] of the result is divisible by 9 is a sanity test—it will not catch ''every'' multiplication error, but is a quick and simple method to discover ''many'' possible errors.

In [[computer science]], a ''sanity test'' is a very brief run-through of the functionality of a [[computer program]], system, calculation, or other analysis, to assure that part of the system or methodology works roughly as expected. This is often prior to a more exhaustive round of testing.

==Use in different fields==
===Mathematical===
A sanity test can refer to various [[order of magnitude|orders of magnitude]] and other simple [[rule of thumb|rule-of-thumb]] devices applied to cross-check [[mathematics|mathematical]] [[calculations]]. For example:
*If one were to attempt to [[square (algebra)|square]] 738 and calculated 54,464, a quick sanity check could show that this result cannot be true. Consider that {{awrap|1=700 < 738,}} yet {{awrap|1=700{{sup|2}} = 7{{sup|2}} × 100{{sup|2}} =}} {{awrap|1=490,000 > 54,464.}} Since squaring positive integers preserves their [[Inequality (mathematics)#Applying a function to both sides|inequality]], the result cannot be true, and so the calculated result is incorrect. The correct answer, {{awrap|1=738{{sup|2}} = 544,644,}} is more than 10 times higher than 54,464.
*In multiplication, {{awrap|1=918 × 155}} is not 142,135 since 918 is divisible by three but 142,135 is not (digits add up to 16, not a [[3#Mathematics|multiple of three]]). Also, the product must end in the same digit as the product of end-digits: {{awrap|1=8 × 5 = 40,}} but 142,135 does not end in "0" like "40", while the correct answer does: {{awrap|1=918 × 155 = 142,290.}} An even quicker check is that the product of even and odd numbers is even, whereas 142,135 is odd.

===Physical===
*[[Dimensional analysis]] may be used as a sanity check of physical equations: the two sides of any equation must be commensurable or have the same dimensions. A person who has calculated the [[Power (physics)|power]] output of a [[automobile|car]] to be 700 [[kilojoule|kJ]] may have omitted a factor, since the unit ''joules'' is a measure of [[energy]], not power (energy per unit time). 
*When determining [[physical property|physical properties]], comparing to known or similar substances will often yield insight on whether the result is reasonable. For instance, most metals sink in water, so the [[density]] of most metals should be greater than [[density of water|that of water]] (~{{val|1000|u=kg/m3}}).
*[[Fermi estimate]]s will often provide insight on the order of magnitude of an expected value.

===Software development===
{{see|Smoke testing (software)}}
In software development, a sanity test (a form of [[software testing]] which offers "quick, broad, and shallow testing"<ref>{{Cite journal |last1=Fecko |first1=Mariusz A. |last2=Lott |first2=Christopher M. |date=October 2002 |title=Lessons learned from automating tests for an operations support system |url=http://www.chris-lott.org/work/pubs/2002-spe.pdf |journal=Software: Practice and Experience |volume=32 |issue=15 |pages=1485–1506 |doi=10.1002/spe.491 |s2cid=16820529 |archive-url=https://web.archive.org/web/20030717041855/http://www.chris-lott.org/work/pubs/2002-spe.pdf |archive-date=17 July 2003}}</ref>) evaluates the result of a subset of application functionality to determine whether it is possible and reasonable to proceed with further testing of the entire application.<ref>{{Cite book |last1=Sammi |first1=Rabia |last2=Masood |first2=Iram |last3=Jabeen |first3=Shunaila |chapter=A Framework to Assure the Quality of Sanity Check Process |date=2011 |editor-last=Zain |editor-first=Jasni Mohamad |editor2-last=Wan Mohd |editor2-first=Wan Maseri bt |editor3-last=El-Qawasmeh |editor3-first=Eyas |title=Software Engineering and Computer Systems |series=Communications in Computer and Information Science |location=Berlin, Heidelberg |publisher=Springer |volume=181 |pages=143–150 |doi=10.1007/978-3-642-22203-0_13 |isbn=978-3-642-22203-0}}</ref> Sanity tests may sometimes be used interchangeably with [[smoke testing (software)|smoke tests]]<ref>ISTQB® Glossary for the International Software Testing Qualification Board® software testing qualification scheme, [https://www.istqb.org/downloads/glossary.html ISTQB Glossary] International Software Testing Qualification Board</ref> insofar as both terms denote tests which determine whether it is ''possible'' and ''reasonable'' to continue testing further.  On the other hand, a distinction is sometimes made that a smoke test is a non-exhaustive test that ascertains whether the most crucial functions of a programme work before proceeding with further testing whereas a sanity test refers to whether specific functionality such as a particular bug fix works as expected without testing the wider functionality of the software.{{citation needed|date=January 2021}}  In other words, a sanity test determines whether the intended result of a code change works correctly while a smoke test ensures that nothing else important was broken in the process.  Sanity testing and smoke testing avoid wasting time and effort by quickly determining whether an application is too flawed to merit more rigorous [[Software quality assurance|QA testing]], but needs more developer [[debugging]].

Groups of sanity tests are often bundled together for automated [[unit testing]] of functions, libraries, or applications prior to [[Merge (version control)|merging]] development code into a testing or [[Trunk (software)|trunk]] version control [[Branching (version control)|branch]],<ref>{{cite journal
 | last = Jørgensen | first = Niels
 | doi = 10.1046/J.1365-2575.2001.00113.X
 | issue = 4
 | journal = Information Systems Journal
 | page = 321
 | title = Putting it all in the trunk: incremental software development in the FreeBSD open source project
 | url = https://webhotel4.ruc.dk/~nielsj/research/publications/freebsd.pdf
 | volume = 11
 | year = 2001}}</ref> for [[Build automation|automated building]],<ref>Hassan, A. E. and Zhang, K. 2006. [http://portal.acm.org/citation.cfm?id=1169218.1169318&coll=&dl=ACM&type=series&idx=SERIES10803&part=series&WantType=Proceedings&title=ASE# Using Decision Trees to Predict the Certification Result of a Build]. In ''Proceedings of the 21st IEEE/ACM international Conference on Automated Software Engineering'' (September 18&nbsp;– 22, 2006). Automated Software Engineering. IEEE Computer Society, Washington, DC, 189–198.</ref> or for [[continuous integration]] and [[continuous deployment]].<ref>{{cite journal
 | last1 = Chasidim | first1 = Hadas
 | last2 = Almog | first2 = Dani
 | last3 = Sohacheski | first3 = Dov Benyomin
 | last4 = Gillenson | first4 = Mark Lee
 | last5 = Poston | first5 = Robin S.
 | last6 = Mark | first6 = Shlomo
 | issue = 2
 | journal = Journal of Information Technology Management
 | pages = 40–54
 | title = The Unit Test: Facing CICD - Are They Elusive Definitions?
 | url = https://jitm.ubalt.edu/XXIX-2/article4.pdf
 | volume = 29
 | year = 2018}}</ref>

Another common usage of ''sanity test'' is to denote checks which are performed {{em|within}} programme code, usually on arguments to functions or returns therefrom, to see if the answers can be assumed to be correct. The more complicated the routine, the more important that its response be checked. The trivial case is checking to see whether the [[Return statement|return value]] of a function indicated success or failure, and to therefore cease further processing upon failure.  This return value is actually often itself the result of a sanity check. For example, if the function attempted to open, write to, and close a file, a sanity check may be used to ensure that it did not fail on any of these actions—which is a sanity check often ignored by programmers.<ref>{{Cite book |last=Darwin |first=Ian F. |url=https://books.google.com/books?id=vweTteq3OLQC&pg=PA19 |title=Checking C programs with lint |date=January 1991 |publisher=O'Reilly & Associates |isbn=0-937175-30-7 |edition=1st ed., with minor revisions. |location=Newton, Mass. |page=19 |quote=A common programming habit is to ignore the return value from fprintf(stderr, ... |access-date=7 October 2014}}</ref>

These kinds of sanity checks may be used during development for debugging purposes and also to aid in [[troubleshooting]] software [[Runtime (program lifecycle phase)|runtime errors]]. For example, in a bank account management application, a sanity check will fail if a withdrawal requests more money than the total account balance rather than allowing the account to go negative (which wouldn't be sane).  Another sanity test might be that deposits or purchases correspond to patterns established by historical data—for example, large purchase transactions or ATM withdrawals in foreign locations never before visited by the cardholder may be flagged for confirmation.{{citation needed|date=January 2021}}

Sanity checks are also performed upon installation of [[Software release life cycle|stable, production]] software code into a new computing [[Runtime system|environment]] to ensure that all [[Coupling (computer programming)|dependencies]] are met, such as a compatible [[operating system]] and [[Linker (computing)|link]] [[Library (computing)|libraries]]. When a computing environment has passed all the sanity checks, it's known as a sane environment for the installation programme to proceed with reasonable expectation of success.

A [["Hello, World!" program]] is often used as a sanity test for a [[Deployment environment#Development|development environment]] similarly.  Rather than a complicated script running a set of unit tests, if this simple programme fails to compile or execute, it proves that the supporting environment likely has a configuration problem that will prevent ''any'' code from compiling or executing.  But if "Hello world" executes, then any problems experienced with other programmes likely can be attributed to errors in that application's code rather than the environment.

The [[Association for Computing Machinery]],<ref>{{cite web|date=2020-11-20|access-date=2023-06-29|url=https://www.acm.org/diversity-inclusion/words-matter|title=Words Matter}}</ref> and software projects such as [[Android (operating system)|Android]],<ref>{{Cite web |date=2022-11-16 |title=Coding with respect |url=https://source.android.com/docs/setup/contribute/respectful-code |access-date=2023-01-23 |website=Android Open Source Project |language=en}}</ref> [[MediaWiki]]<ref>{{Cite web |title=Inclusive language/en-gb - MediaWiki |url=https://www.mediawiki.org/wiki/Inclusive_language/en-gb |access-date=2023-01-23 |website=www.mediawiki.org |language=en}}</ref> and [[Twitter]],<ref>{{Cite web  |title=Twitter Engineering|url=https://twitter.com/twittereng/status/1278733305190342656 |access-date=2023-01-23 |website=Twitter |language=en-GB}}</ref> discourage use of the phrase ''sanity check'' in favour of other terms such as ''confidence test'', ''coherence check'', or simply ''test'', as part of a wider attempt to avoid [[ableist]] language and increase [[Inclusion (disability rights)|inclusivity]].

==See also==

* [[Certifying algorithm]]
* [[Checksum]]
* [[Fermi problem]]
* [[Mental calculation]]
* [[Proof of concept]]

==References==
{{Reflist}}

{{standard test item}}

[[Category:Software testing]]
[[Category:Error detection and correction]]