2. Object Oriented Software testing Activities. Figure 1 the various testing activities in SDLC

Transcription

1 odelng of Object Orented oftware Testng ost Dnesh Kumar an, onuddn Ahmad 2 Faculty of omputng and nformaton Technology, ohar nversty 2Faculty of Busness, ohar nversty P.O. Box:, P.. 3, ohar, ultanate of Oman Tel: Ext: 25, oble: , e_mal: dnesh@soharun.edu.om, mahmad@soharun.edu.om Abstract An effort s made to develop a cost model n ths paper for the object orented software testng process. The software must be tested to an extent so that before releasng t. s assured that the falures rsks have been mnmzed. There s a trade-off between testng cost and release polces. There may be varous factors affectng the total software testng cost. n ths paper, an object orented software testng cost model s presented whch can be used to determne the optmal release polces for the software. Varous software cost factors are consdered n ths paper such as the cost of object orented testng and removng detected errors. The error whch ncurs lot of money and tme n the software development process must be ncluded as removal cost whch s a stochastc process. Key Words Object Orented ystems, Testng, ost, Error, and Bug.. ntroducton Once the software developng process (usually ncludng the followng four phases: analyss, desgn, codng, and testng s completed, the software company releases the software product to market and obtans some profts n return f the software functons successfully (l, A. et al Durng the developng process, the company has to pay for such expendtures as the labor fee, the cost of developng, and the cost of testng, and so on. Therefore there s always testng cost assocated whenever we want to make qualty software. ustomer satsfacton depends on the qualty of the software, hgher the qualty hgher the customer satsfacton but fnally the customer has to pay for all the expendtures occurred durng the software testng. Therefore t becomes the moral duty of software developng company to justfy the software testng cost n terms of software qualty acheved. Therefore t s mportant to have an estmaton of software testng cost n some mathematcal expresson. n the software development process, the manager must reasonably decde when to stop testng and release the software system to the user. Ths decson problem s called optmal software-release (Ohtera H. et al The pressure of delverng hgh qualty software products calls for a better understandng of the software development process and mproved software models (Koch H.. et al.983. The cost of software testng can be hgh, and n many cases t s exceedng 30% of the overall software development costs for the project (Hetzel et al Ths places ncreased pressure on testng team. The software products whch are developed usng object orented concepts needs a decson as when to stop testng based on some crtera. We develop a mathematcal expresson for all testng costs that may occur durng testng and removng errors n object orented development. n order to mprove the qualty of software products, testng serves as the man tool to remove faults n software products. There wll be exponental ncrease n the cost when qualty enforcement s carred out at the refnement stage n the software development process refnement (Pham H. et al Therefore, t s usually very mportant to determne when to stop testng based on the cost assessment. 2. Object Orented oftware testng Actvtes Fgure the varous testng actvtes n DL

2 n object orented software development lfe cycle the varous phases are shown n Fgure. The varous actvtes assocated wth these phases are also shown here. Actvtes are the thngs that are expected from the desgners and what they should be dong. An actvty takes nputs and produces outputs. These nputs and outputs are referred to as artfacts. The artfacts that act as an nput to a partcular actvty could be a use case, whle the output from that actvty could be a class dagram etc. 3. oftware testng cost oftware systems are prone to falures and the falure can occurs any tme or even t can be at any random tmes. Falures are caused by the faults n the systems. oftware testng s very crtcal part of the software because t helps n reducng the chances of falures. The cost of software development process has bg porton for the software testng. Accurately estmatng the costs of all phases of the software development process as well as software testng have become more mportant. nce resources are lmted, t s crtcal to determne how they should be allocated throughout the software lfe-cycle (Brand L.. et al Varous tools are also beng developed to estmate software testng costs. nce the man objectve of testng s to mprove the software qualty. Nether process mprovements n development nor n testng alone can guarantee qualty mprovement. Harter and laughter (Harter, D. E. et al state that t s an unresolved ssue how software qualty can be mproved. Qualty can be tested nto software products or t can be desgned or bult nto the products (laughter,. A., et al Accordng to Harter and laughter (Harter, D. E. et al. 2000, software qualty s rather desgned than tested nto products. Both desgn and testng have a sgnfcant nfluence on product qualty. The software cost estmaton should be done correctly. ome framework lke (Grmstad,. et al can be used for correctly estmatng the cost.here we wll try to model the object orented testng cost. ost estmaton (Dolado J.J., 200 can be erroneous and some strategy lke (Lederer A.L. et al. 988 can be used to estmate the cost estmaton errors. Varous researchers have also used experments to predct the project costs usng dfferent algorthmc technques (Banker, R. D. et al. 989, (Kemerer,. F. 987, (Kusters, R. et al. 990, (cabe; 976. These can also be used for estmatng the cost of testng the software. Fgure 2. The ost Dagram for Testng of Object Orented ystems. ost odel Object-orented testng needs to test all the aspects of software development process. An object orented software development conssts of varous phases n ts development cycle. Each phase of software development needs to be tested for correctness. Object orented softwares are developed usng L specfcatons. These L dagrams (Booch, G. et al. 998 can themselves be used to automatcally generate and select test cases (Kansomkeat,. et al (Offutt, J. et al.999. A use case s a set of scenaros that descrbes an nteracton between a user and a system. se case dagrams are related and ths relatonshp s vsble among actors and use cases. The two man components of a use case dagram are use cases and actors. There may be varous steps n whch use cases may be tested (Booth, G., 986. Frst of all the use cases are requred to be tested syntactcally to ensure that the use case descrptons descrbes the correct and proper nformaton. We must fnd answers of questons lke: s t complete? s t correct? s t consstent? After checkng for the syntax next step s doman testng. Here we need to fnd a doman expert. Agan, we need to ask the same questons: s t complete? s t correct? s t consstent? After that the next step s traceablty testng. Traceablty testng s to make sure all the requrements especally functonal requrement are there n the use cases and from the use cases to the requrements back. t should be complete, correct and consstent and ths should be tested. Let the number of use cases s N u and any th use case takes T tme n testng and the cost assocated wth testng one use-case testng be K u then total cost of use case testng s gven by: N u K u T use case = ( lass dagrams n object orented systems are descrpton of the types of objects n object orented systems and ther relatonshps wth each other. lass dagrams helps n modelng the class contents and class structures. lass

3 Dagrams uses desgn tools and elements of the class. lass dagrams express three dfferent aspects of the systems lke conceptual, specfcaton, and mplementaton. lasses consst of three man tems whch are: a name, attrbutes, and operatons. All the three are needed for testng the class concept and the cost of testng a class dagram wll depends on the followng tems.. The number of classes n a class dagram let t be N. 2. The number of relatonshps of each of the class wth other classes, let any class s havng relatonshps wth n other classes. 3. The number of attrbutes and the number of operatons that each class has, let a class has total number of attrbutes A and total number of operatons O. o the cost of testng a class dagram wll be: N lass Dagram =N K n (2 The other major component of object orented systems whch should be tested serously s nteracton dagrams, whch are responsble for modelng the behavor of use cases by descrbng the way groups of objects nteract to complete the task n the object orented systems. The two major knds of nteracton dagrams are sequence dagrams and collaboraton dagrams. nteracton dagrams are helpful n descrbng the behavor of objects n the use cases. nteracton dagrams provde nformaton for how the objects collaborate behaves n the object orented systems.. equence dagrams demonstrate the behavor of objects n a use case by descrbng the objects and the messages they pass. There may be a number of sequence dagrams. Let the number of sequence dagrams to test s N and the cost assocated wth testng one sequence dagram s K so the total cost of testng sequence dagrams s gven as: N equence Dagram = K n (3 ollaboraton dagrams descrbes the relatonshp between objects and the order of messages passed between objects. The objects are lsted as cons and arrows ndcate the messages beng passed between them. The numbers next to the messages are called sequence numbers. As the name suggests, they show the sequence of the messages as they are passed between the objects. Let the number of collaboraton dagrams s N l and the cost assocated wth one collaboraton dagram s K l then the total cost of testng collaboraton dagrams s: K l ollaboraton Dagram = K l n ( tate dagrams are used to descrbe the behavor of a system. tate dagrams descrbe all of the possble states of an object as events occur. Each dagram usually represents objects of a sngle class and tracks the dfferent states of ts objects through the system. The state dagram testng cost wll depend on the number of state dagrams N t and the number of states n each state dagram, let number of states n th state dagram s n. N t tate Dagram = K t n (5 Actvty dagrams descrbe the workflow behavor of a system. Actvty dagrams are smlar to state dagrams because actvtes are the state of dong somethng. The dagrams descrbe the state of actvtes by showng the sequence of actvtes performed. Actvty dagrams can show actvtes that are condtonal or parallel. The cost of testng actvty dagrams wll depend on number of actvty dagrams to be tested n program and the number of actvtes n each of the actvty dagrams. Let there be total N A actvty dagrams ate there and number of actvtes n th actvty dagram s n N A K A n Actvty Dagram = (6 oftware testng s done at varous levels, so the dfferent software test cost s assocated wth these varous levels. These are bascally unt testng, ntegraton testng and system testng. nt testng s concerned wth verfyng the behavor of the smallest solated components of the system. Typcally, ths knd of testng s performed by developers or mantaners and nvolves usng knowledge of the code tself. n practce, t s often dffcult to test components n solaton. omponents often tend to rely on others to perform ther functon. n object orented envronment the unt s a class. ntegraton testng s focused at the verfcaton of the nteractons between the components of the system. The components are typcally subjected to unt testng before ntegraton testng starts. A strategy that determnes the order n whch components should be combned usually follows from the archtecture of the system. ystem testng occurs at the level of the system as a whole. On the one hand, the system can be valdated aganst the non-functonal requrements, such as performance, securty, relablty or nteractons wth external systems. On the other hand, the functonalty mplemented by the system can be compared to ts specfcaton (Farren D, 996. Once the software developng process (usually ncludng the followng four phases: analyss, desgn, codng, and testng s completed, the software company releases the software product to market and obtans some profts n return f the software functons successfully. The product may not be good enough f all the metrcs nvolved n software test are not well tested (Kan,.H. et al. 200.

4 5. Testng cost model for object orented systems How the cost of object orented software vares? What are the factors on whch t depends on? Our proposed model tres to fnd out the answer of these questons. There are varous other models (Yang,.. et al. 995 (Goel A.L. et al.979] n lterature whch model the optmum release tme for the software. There may be software release polces determned by company management for ths. o ths estmaton of software test cost for object orented envronment s a crtcal ssue (Page T., et al, 989. Our model of software testng broadly dvdes the whole testng process as accordng to ts testng levels. We have taken nto consderaton the factors nto consderaton whch affect n each of these phases. Our model conssts of:. ost to perform testng E (. 2. ost ncurred n removng errors E 2 (. The odels assumptons are as follow: The cost to perform testng s proportonal to the testng tmes. Errors found durng testng consst of two parts - the determnstc part and the ncremental random part of the error. The testng of a class conssts of testng all of the class components and ts assocaton wth other classes. Notaton: : oftware unt testng cost per unt tme 2 : oftware ntegraton testng cost per unt tme 3 : oftware system testng cost per unt tme : determnstc cost to remove each error per unt tme durng unt testng phase 5 : determnstc cost to remove each error per unt tme durng ntegraton testng phase 6 : determnstc cost to remove each error per unt tme durng system testng phase T : Tme ncurred n unt testng T : Tme ncurred n ntegraton testng T : Tme ncurred n system testng w : random varable of cost to remove errors durng unt testng w : random varable of cost to remove errors durng ntegraton testng w : random varable of cost to remove errors durng system testng : Total number of classes w w testng m ( T : expectaton value of varable w n unt testng : expectaton value of varable w n ntegraton : average number of falures n all classes detected durng the unt testng tme T a. Testng ost: ncludes testng actvtes: preparng test cases, runnng them and analyzng results. E (= T + 2 T + 3 T (7 where T + T + T = T b. Error removal cost: Errors are removed as soon as they are dscovered. We wll fnd out the expressons of error removal cost at varous levels of testng. These levels are unt testng, ntegraton testng and system level testng. f we consder the testng at unt level, then here the unt s class. Let us consder that there are numbers of classes whch are tested for errors. Testng of a class means we have to test each of ts methods. Accordng to assumpton (2 above, the cost to remove errors durng the testng phase s a random varable and conssts of two parts - the determnstc part, say, and the ncremental random part, whch reflects the dffcultes of dfferent errors. (t, t>0 s countng process of errors detected durng testng phase and can be consdered a stochastc renewal process. The cost of removng j th error n a class: j = + W The cost of removng all errors from class any class s gven by: N ( T j w ( 8 Where (N (t >0 s the countng process of errors detected durng testng of class L. o N (T s the total number of errors dscovered n tme T. Expected total cost to remove all detected errors n a class durng perod [0,T, E 2 (T s gven by: 2 N ( T T E w E (9 j f there are total classes, then cost of removng all errors from classes: E ( T E N ( T j w N E w. N n n j n E w. N n j n

5 ost ncurred n ntegraton test ost ncurred n nt Testng. n w N n n N n n n n. N n w E( N w m w T m w [ m( T w ] where T T T T m( T and s average number of falures n all classes detected durng the unt testng tme T. The cost ncurred n error removal durng ntegraton testng: the cost of removng th error 5 w E ( T E E N ( T N ( T ( 5 w N ( T E ( 5 w. n n n E ( 5 w. n n n. n5 w n N u = N t K u T K t n so the total cost to remove errors N +N N A + K n K A m + N + K n K l + K l n [ m( T w ] 5m ( T w 6 m ( T c. mpact of Testng cost coeffcent n unt test the cost of removng all errors from a class depends on cost factor and the random factor W. From the expresson obtaned for total cost ncurred n unt test t s clear that total cost s lnear wth. To plot the graph between total unt test cost and We have taken =20, m ( 0 and 50 T ts clear that for more number of classes the cost would be ncreased wth that factor. t s evdent that the cost of testng s ncreasng wth the testng tme and number of faults appearng n the software w ost Factor (ORE: Wpro oftware Testng nt d. mpact of Testng cost coeffcent 5 + eres2 eres The cost ncurred n ntegraton testng depends on cost factor 5. From the expresson obtaned for total ntegraton testng cost t s observed that t s lnear wth w 5 n. n w n n n E( 5 m ( T 5 w mlar expresson s obtaned for system level testng: E ( T 6 w m ( T w ost factor 5 (ORE: Wpro oftware Testng nt eres

6 6. oncluson The testng cost n object orented software system has a great mpact on decdng the release tme for the software. The more we test the cost ncurred wll also ncrease more. But the overall completeness of software wll be sgnfcantly ncreased. Therefore there must be a trade-off between testng cost and tme. Our proposed model can be used for predctng the total cost ncurred n testng and removng errors and bugs from object orented systems. References:. Ohtera H., Yamada, 990, Optmum oftware-release Tme onsderng an Error- Detecton Phenomenon durng Operaton, EEE transactons on relablty. Vol. 39, no. 5. pp Koch H.., Kuba P., 983, "Optmal release lme of computer software".eee Trans. oftware Engneerng, vol E-9, pp Yang,.. and hao A., 995, "Relablty- Estmaton & toppng-rules for oftware Testng, Based on Repeated Appearances of Bugs," EEE Transacton on Relablty, 2, pp Goel A.L.and Okumoto K, 979, Tme- Dependent Error-Detecton Rate odel for oftware Relablty and Other Performance easures," EEE Ttans. Relablty, Vol. R- 28, No. 3, pp Page T., et al, 989, "An Object Orented odellng Envronment," Proceedngs of the Fourth Annual A onference on Object Orented Programmng ystems, Languages and Applcatons (OOPLA. 6. Farren D, 996, The Economcs of ystem Level Testng, PhD thess, Brune nv., xbrdge,.k. 7. Hetzel, Wllam., 988, The omplete Gude to oftware Testng, econd edton, John Wley & ons, NY A. 8. Pham H. and Zhang X., 999, oftware release polces wth gan n relablty justfyng the costs,.annals of oftware Engneerng 8, pp l, A., hmel,. F., 2000, Gottumukkala, R., and Zhang, L An ntegrated cost model for software reuse. n Proceedngs of the 22nd nternatonal onference on oftware Engneerng (Lmerck, reland, June 0 -, E '00. A Press, New York, NY, pp Booth, G., 986, Object Orented Development, EEE Transactons on oftware Engneerng, E-2, February, pp Kan,.H., Parrsh, J., and anlove, D., 200, n-process metrcs for software testng, B ystems Journal, Vol. 0, No., 200, p Harter, D. E. and laughter,. A Process maturty and software qualty: a feld study. n Proceedngs of the Twenty Frst nternatonal onference on nformaton ystems (Brsbane, Queensland, Australa. nternatonal onference on nformaton ystems. Assocaton for nformaton ystems, Atlanta, GA, pp Kansomkeat,. and Rvepboon, W Automated-generatng test case usng L statechart dagrams. A nternatonal onference Proceedng eres, vol. 7. outh Afrcan nsttute for omputer centsts and nformaton Technologsts, pp Booch, G., Rumbaugh, J., and Jacobson, The nfed odelng Language ser Gude. Object Technology eres. Addson Wessley Longman, nc. 5. Offutt, J., and Abdurazk, A Generatng test cases from L specfcatons. n Proceedng of the 2nd nternatonal onference on the nfed odelng Language (L99, Fort ollns, O, October, laughter,. A., Harter, D. E., and Krshnan,.. 998, Evaluatng the ost of oftware Qualty. ommuncatons of the A,, 8 (998, pp Grmstad,. and Jørgensen, A framework for the analyss of software cost estmaton accuracy. n Proceedngs of the 2006 A/EEE nternatonal ymposum on nternatonal ymposum on Emprcal oftware Engneerng (Ro de Janero, Brazl, eptember 2-22, EE '06. A Press, New York, NY, pp Brand L.. and Weczorek., 2002, "Resource estmaton n software engneerng," n Encyclopeda of software engneerng, J. J. arcnak, Ed., 2nd ed. New York: John Wley & ons, pp Lederer A.L. and Prasad, J. 988 "A causal model for software cost estmatng error," EEE Transactons on oftware Engneerng, vol. 2, no. 2, pp Dolado J.J., 200, "On the problem of the software cost functon," nformaton and oftware Technology, vol. 3, no., pp artn, R. 988 "Evaluaton of urrent oftware ostng Tools," oftware Eng. Notes, vol.3, no.3, pp Banker, R. D. and Kemerer,. F cale Economes n New oftware Development.

7 EEE Trans. oftw. Eng. 5, 0 (Oct. 989, pp Kemerer,. F An emprcal valdaton of software cost estmaton models. ommun. A 30, 5 (ay. 987, pp Kusters, R., van Genuchten,. J., and Heemstra, F. J Are software costestmaton models accurate. nf. oftw. Technol. 32, 3 (Apr. 990, pp cabe; 976, A omplexty easure, EEE Transactons on oftware Engneerng, 2, pp