Qualitätssicherung von Software (SWQS)

Qualitätssicherung von Software (SWQS)

Prof. Dr. Holger Schlingloff

Humboldt-Universität zu Berlinund

Fraunhofer FOKUS

15.7.2014: Modellbasierter Test (Jaroslav Svacina)

http://www.hu-berlin.de/index.html

Folie 3H. Schlingloff, Software-Qualitätssicherung

Specification-based Testing

• Constructing the test suite from the specification as opposed to constructing it from the implementation

(= code-based testing)

code-based testing cannot detect missing requirements specification-based testing cannot detect additional

(unspecified) features

specifiedbehaviour

implementedbehaviour

testedbehaviour


Model-based Testing

• SUT is compared to a formal model (requirements)

• Automation of test case design• Early validation of requirements• Traceability• Easy maintenance of test suites for regression

testing


Model-based Design and Model-based Testing

• Often: same syntax, different pragmatics e.g. test cases can be formulated in Java e.g. system spec can be formulated with LTL

Requirements

System Spec Test Spec

System Model

System Impl. Test Cases

Test Model


System models vs. Test models

• Models can help in the development of complex systems

• The more concrete the formalism, the closer it is to an implementation executable code may be generated from state

diagrams We might add additional information such as timing,

communication, variables and such.

• Test model as opposed to implementation model describes properties of the targeted system not aiming at a complete description of the system not aiming at the generation of executable code


Model-based Testing


Model-based Testing


Modelling

• Describe system requirements for test generation

• High abstraction level


Modelling Notations

•Pre/Post (state based) notations State variables, operations

(pre-/postcondition) B, SpecExplorer (c#), UML OCL

•Transition based notations Focus on describing the transitions between

states of the system UML State Machines, Simulink State Flow

•…


Example: A Kitchen Toaster

•A toaster what is the

technical process? what are the states,

events and signals of the (technical) process?

what are the boundaries of the system? which information processing is to be done? what are the interfaces between technical

system and information processing component?


Modeling the Toaster

• User Interfaces: turning knob, side lever, stop button

• Internals: heating element, retainer latch

• Extra: defrost button

• First approach: timing is neglected (timer event)

• Advanced approach: timing depends on various parameters


Toaster – Simple State Machine


Toaster – Hierarchical Design


Toaster – with Variables


Test Generation


Test Generation

•Algorithm Graph traversal yields abstract test cases

- Dijkstra shortest path algorithm

- Depth-first and breadth-first search

Evolutionary algorithm

•Model Transformation

•Static analysis for input parameters Partition Testing Classification tree method Boundary value analysis


All-States with Dijkstra and DFS


Evolutionary Test Generation


Test Selection


Test Generation from State Machines

•Define a test case to be any execution path•How to generate such paths? How many

paths to generate? When to stop testing? Coverage criteria e.g.

all-states all-transitions all-transition-pairs all-n-paths

•Test goal: one particular item to be covered


Tests for State Machines

• For a state machine, a test case is just a finite sequence of external triggers and actions

• A test goal is a particular entity of the state machine (region, pseudostate, transition, n-path, …; for each test and goal it is defined whether the test reaches this goal

• The coverage of a test suite is the percentage of reached test goals the coverage can either be measured during the

execution of a test suite, or statically before execution


Coverage for State Machines

• common coverage criteria for UML state machines all-states all-transitions all configurations: all combinations of parallel substates n-transition-coverage means all reachable transition

sequences of length n are covered (esp.: pairs) All-loop-free-paths All-n-loop-paths decision coverage, condition coverage, MC/DC, ...

• all-requirements


Szenarien als Testselektionskriterium• Schwierige, nicht ausreichende Möglichkeiten zur

Beschreibung der Testselektionskriterien

• Einflussnahme der Domänenexperten auf den Testselektionsprozess


Szenarien als Testselektionskriterium


Automated Test Generation Tools

• More than a dozen commercial and experimental research tools available

• Usually quite costly (>10K€ per license)

• Mostly from UML State Machines

• Comparison e.g. by mutation analysis


Conformiq


ParTeG – Partition Test Generator

• Since we didn’t like the pricing, and wanted to experiment with different technologies, a Ph.D. student built his own… http://parteg.sourceforge.net/

• UML class & state transition diagrams, connected by OCL • Plugin for Eclipse, supports XMI import / export

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Qualitätssicherung von Software (SWQS)

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