Model-based testing (MBT) is a promising testing method with advantages like exhaustive exploration and high maintainability. However, one notable downside is that the generated tests usually contain much unnecessary noise. This noise can present itself as superfluous actions that bear no effect on test outcome — worsening comprehensibility and inflating test size. Generalpurpose minimization techniques like delta debugging have been successful in minimizing similar input before. The process involves removing elements that are redundant for satisfying given criteria, e.g., that a test still identifies a specific fault. In this thesis, we formulate the modmin algorithm which makes use of a hierarchical delta debugging approach to minimize sequences generated with Modbat — an open source MBT tool based on the extended finite-state machine (EFSM). One after the other, the algorithm attacks three common sub-structures found within the generated tests: model instances, loops, and transitions. To evaluate the work, we extended Modbat with modmin and applied it to tests generated from a set of ten models of varying complexity. The results show that modmin is very proficient at minimizing the tests generated from our model set and that it does so at a negligible cost. / Modellbaserad testning är en lovande teknik med fördelar som uttömande sökning och hög underhållbarhet. En nackdel är däremot att de genererade testfallen tenderar att innehålla onödig information. Ett testfall ska, med fördel, vara så kort och koncist som möjligt, och överflödiga instruktioner förvärrar både testbegriplighet och teststorlek. Minimeringsstrategier som delta debugging har med goda resultat används för att minimera liknande datastrukturer tidigare. Processen innebär vanligtvis att man plockar bort element som inte är nödvändiga för att särskilda kriterier ska vara uppfyllda. Exempelvis att ett test fortfarande identifierar samma fel som innan. I det här verket formulerar vi och implementerar modmin-algoritmen, en algoritm som bygger på hierarkisk delta debugging för att minimera testfall generade med det modellbaserade testningsverktyget Modbat. En efter en attackerar vår algoritm tre vanliga delstrukturer som vi har identifierat i Modbats testfall: modellinstanser, slingor, och individuella övergångar. Vi utvärderade arbetet genom att utöka Modbats öppna källkod med modmin och sen minimera testfall genererade från tio olika modeller av varierande komplexitet. Resultaten visar att modmin klarar av att minimera testfall generade från alla våra modeller och att det bara tillför en försumbar kostnad vad gäller systemresurser eller körtid.

Verifying the reliability and functionality of a complex system like a trading system is highly demanding since failure in such a system can cause serious economic problems. Automated random testing is a good solution to find new and rare failures in such a system. Test cases in random testing usually contain a long sequence of actions that debugging them manually to find the root cause of the failure is a very boring and tiresome task. This thesis aims to create a model for automating the task of the debugging to reduce the failed test case to an equivalent test case that only contains relevant actions that together cause the failure. Delta debugging is the core algorithm of the model that simplifies a failed test case by successive testing. The target of the project is TRADExpress system of Cinnober Financial Technology AB. The model is integrated to the random testing framework of the TRADExpress system.

With modern computer systems becoming more and more complicated, theimportance of rigorous testing to ensure the quality of the product increases.This, however, means that the cost to perform tests also increases. In orderto address this problem, a lot of research has been conducted during thelast years to find a more automated way of testing software systems. Inthis thesis, different algorithms to automatically explore and test a systemhave been implemented and evaluated. In addition to this, a second setof algorithms have been implemented with the objective to isolate whichinteractions with the system were responsible for a failure. These algorithmswere also evaluated and compared against each other. In the first evaluationtwo explorers, which I called DeBruijn and LStarExplorer, were consideredsuperior to the other. The first used a DeBruijn sequence to brute forcea solution while the second used the L*-algorithm to build an FSM overthe system under test. This FSM could then be used to provide a moreaccurate description for when the failure occurred. The result from thesecond evaluation were two reducers which both tried to recreate a failureby first applying interactions performed just before the failure occurred. Ifthis was not successful, they tried interactions further and further away, untilthe failure was triggered. In addition to this, the thesis contains descriptionsabout the framework used to run the different strategies. / D ̊a v ̊ara moderna datasystem blir allt mer komplicerade,  ̈okar detta st ̈andigtbehovet av rigor ̈osa tester f ̈or att s ̈akerst ̈alla kvaliteten p ̊a den slutgiltiga pro-dukten. Det h ̈ar inneb ̈ar dock att kostnaden f ̈or att utf ̈ora testerna ocks ̊ao  ̈ kar. F ̈or att f ̈ors ̈oka hitta en l ̈osning p ̊a det h ̈ar problemet har forsknin-gen under senare tid arbetat med att ta fram automatiserade metoder atttesta mjukvarusystem. I den h ̈ar uppsatsen har olika algoritmer, f ̈or attutforska och testa ett system, implementerats och utv ̈arderats. D ̈arut ̈overhar ocks ̊a en grupp algoritmer implementerats som ska kunna isolera vilkainteraktioner med ett system som f ̊ar det att fallera.  ̈aven dessa algoritmerhar utv ̈arderats och testats mot varandra. Resultatet fr ̊an det f ̈orsta ex-perimentet var tv ̊a explorers, h ̈ar kallade DeBruijn och LStarExplorer, somvisade sig vara b ̈attre  ̈an de andra. Den f ̈orsta av dessa anv ̈ande en DeBruijn-sekvens f ̈or att hitta felen, medan den andra anv ̈ande en L*-algoritm f ̈or attbygga upp en FSM  ̈over systemet. Den h ̈ar FSM:en kunde sedan anv ̈andasf ̈or att mer precist beskriva n ̈ar felet uppstod. Resultatet fr ̊an det andraexperimentet var tv ̊a reducers, vilka b ̊ada f ̈ors ̈okte  ̊aterskapa fel genom attf ̈orst applicera interaktioner som ursprungligen utf ̈ordes percis innan feletuppstod. Om felet inte kunde  ̊aterskapas p ̊a detta s ̈att, fortsatte de medatt applicera interaktioner l ̈angre bort tills felet kunde  ̊aterskapas. Ut ̈overdetta inneh ̊aller uppsatsen ocks ̊a beskrivningar av ramverken som anv ̈andsf ̈or att k ̈ora de olika strategierna.