Model-based Testing Principles
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The document discusses model-based testing principles. It defines what a model is and why modeling is important. It explains that model-based testing extracts test cases from models of a system to validate conformance to specifications. The document outlines different types of models that can be used for model-based testing, including UML diagrams. It also describes key activities in model-based testing like test selection, execution, and evaluation.
Model-based Testing Principles
- 1. Università degli Studi dell’Aquila L22. Model-based Testing (Principles) Henry Muccini DISIM, University of L’Aquila www.henrymuccini.com, henry.muccini@univaq.it
- 2. Copyright Notice The material in these slides may be freely reproduced and distributed, partially or totally, as far as an explicit reference or acknowledge to the material author is preserved. Henry Muccini
- 4. Agenda Modeling MBT: →Why? →Modelsfor MBT →UML-based Testing ─ Testing activities
- 5. AGENDA Modeling Model-based testing Why? Models for MBT UML-based Testing
- 6. Modeling: there is not just programming What is a model: →A model is a simplification of the reality →The reality is abstracted, since it is too complex Why modeling →Models are built for a better understanding of the system under development Everything is a model ?!?
- 10. Other Software Models (Web models)
- 11. … other software models…
- 12. … and many others… Pilot Pilot CoPilot CoPilot Multifunction Multifunction Multifunction Multifunction Display1 Display2 Display1 Display2 Display Display Display Display Processor Processor Processor Processor High speed network High speed network Mission Mission Mission Processor Processor Processor 1553 bus 1553 bus Auto-Pilot GPS Nav Radio
- 13. Model Driven Development (MDD) Models are becoming first core assets in Software Engineering/Architecting: →models are primary artifacts retained as first class entities that can be analyzed and manipulated by means of automated tools →the focus moves from writing and sharing documents to writing and sharing models.
- 14. From Document Driven to Model Driven
- 15. Models in MDD Models in MDD can be used for: →Documenting design decisions →Guiding the coding phase →For analyzing and validating design choices ─ by complementing traditional code-level analysis techniques
- 16. Why modeling? For Documenting and Analysis
- 17. What is MBT? It consists in: →ExtractingTest Cases from the Model →Run the test case over the system implementation Purpose: →Tovalidate the implementation conformance to the model ─ The model itself is the oracle, i.e., it represents the expected behavior
- 18. Model-based Testing A model based testing approach accepts two main inputs →a model of the software under test, →a set of test generation directives which guide the test cases selection and outputs a test specification →which includes a set of stimuli the tester should introduce in the system together with expected responses
- 19. Modeling for testing Essentially, we need (at least) a behavioral model of the software system: →Labelled Transition System →StateCharts →UML State of Sequence Diagrams →IOLTS →Finite State Automata →…
- 20. The base-line technique for designing test cases →Timely ─ Often useful in refining specifications and assessing testability before code is written →Effective ─ finds some classes of fault (e.g., missing logic) that can elude other approaches →Widely applicable ─ to any description of program behavior serving as spec ─ at any level of granularity from module to system testing. →Economical ─ typically less expensive to design and execute than structural (code-based) test cases (C) 2007 MAURO PEZZÈ & MICHAL YOUNG
- 21. Program code is not necessary →Only a description of intended behavior is needed →Even incomplete and informal specifications can be used ─ Although precise, complete specifications lead to better test suites Early functional test design has side benefits →Often reveals ambiguities and inconsistency in spec →Useful for assessing testability ─ And improving test schedule and budget by improving spec →Useful explanation of specification ─ or in the extreme case (as in XP), test cases are the spec (C) 2007 MAURO PEZZÈ & MICHAL YOUNG
- 22. Different testing strategies (functional, structural, fault-based, model-based) are most effective for different classes of faults Functional testing is best for missing logic faults →A common problem: Some program logic was simply forgotten →Structural (code-based) testing will never focus on code that isn’t there! (C) 2007 MAURO PEZZÈ & MICHAL YOUNG
- 23. Modeling for testing Such a model can be produced: 1. Through a formal specification language ─ Typically referred as formal testing 2. Through a diagrammatic (visual) notation ─ Typically referred as UML-based Testing
- 24. 1. MBT based on Formal Specifications Since the 80’s, many specification-based testing approaches have been proposed, based on formal languages such as →Z, VDM, CSP, CCS, LOTOS, SDL, and Petri Nets. More recently: →Based on dynamic behavior: ─ FSM-based (Bochmann&Petrenko, Lee&Yannakis, …) ─ LTS-based (Brinksma&Tretmans, Jard&Jeron …) →Focussing on static aspects, ─ ADT theory (Bernot&Gaudel…) ─ Z-based (Hierons…)
- 25. Formal Specification-based Testing TorX (Côte de Resyste) → on-the-fly test generation and execution → random → LOTOS and Promela TGV (IRISA - Rennes) →derives tests in TTCN from LOTOS or SDL → uses test purposes TVEDA (CNET - France Telecom) → derives TTCN tests from SDL specification
- 26. 2. MBT based on the UML UML State-machine based testing: →which might require the translation of the UML diagrams into an intermediate formal description Scenario-based testing: →based on the use of opportunely annotated UML Sequence Diagram State-based and Scenario-based: combine the use of interaction diagrams and state diagram, possibly annotated with further (formal) information (e.g. OCL)
- 27. Model-based Testing: the overall idea From Leila Naslavsky Advancement report
- 28. AsmL L TESTO OR UMLAU UT Model-based Testing Approaches UMLTe est AGEDI IS TOTEM M SOOT TF COW-SU UITE SCENTO OR SeDiTe eC UCSC-Sy ystem
- 29. Main Testing Activities Test Selection/Generation: →it consists in selecting a suitable and finite set of test cases from the possibly infinite set; Test Execution and Evaluation: →it consists in executing the code accordingly to the selected test cases and comparing real and expected results;
- 30. Test Selection A test case, in MBT, is typically a possible “scenario” →In scenario-based testing: ─ A scenario itself is an abstract test case →In state-based testing ─ Execution flows are extraced from the state machine and represent a test case ─ MB coverage criteria are applied on this model
- 31. Test Case Selection Abstract Test case = path over the LTS/FSM, corresponding to sequences of events ─ They are not “concrete” test cases, but abstract (depending on the specification) →Concrete Test cases = mapping asbtract test cases into execution statements to be launched
- 32. Test Case Selection Model of the Test system directives inSD 1 1 C1 C2 m9 m1 Test specification outSD1 2 C1 C2 C3 m9 m3 m8 m1
- 34. Test Execution It consists in running the test cases on the system implementation →So to compare the real execution with the expected behavior
- 35. MBT practical concerns Traceability, i.e. relating the abstract values of the specification to the concrete values of the implementation. Execution, i.e. forcing the Implementation Under Test (IUT) to execute the specific sequence of events that has been selected.
- 36. Testing and Industry In order to be suitable for industrial needs a testing approach has to emphasize the following qualities: →Usability ─ Not ad-hoc models →Timeliness ─ Soon and even incomplete Opposed to →Tool support accuracy Goal of a suitable testing approach should be “to improve the test results accuracy without sensibly raising the testing effort”
- 37. MBT Tools There are some automated tools for MBT: →Telelogic Tau and Tau Tester →Leirios Test Designer →Conformiq Qtronic →Rhapsody Test Conductor and Automatic Test Generation →AGEDIS
- 38. MBT in industry: challenges and issues As remarked by Alan Hartman in his 2006 speech at ISSTA: →“Only 1% of industry uses it” Why?
- 39. Why? The main reasons I foresee: →Model2Code (and viceversa) traceability problems →modeling is not yet so widely recognized as part of the development process. ─ Legacy systems →because of tool/service problems →cost/effectiveness is still under exploration
- 40. Conformiq: Two models are required in Input •SutModel.Java (in QML) •SutModel.xmi (Graphical Notation)
- 41. QML Just like Java, QML consists of variables and expressions, all strictly typed and known before the compilation. The types are divided into the same three groups that Java has: primitives, references and values
- 42. QML QML extends Java with: Records Ports System block State machines
- 45. Coverage Figure 5 – The Coverage Editor window