6. Model based testing (A)

Author

Affiliations

Gabor Arpad Nemeth

Eötvös Loránd University (Hungary)

Original material

This page is a work-in-progress, the original materials can be accessed at ik-elte-sharepoint

Course material

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Agenda

Short agenda:

1. Theory background of MBT (Model-based testing)
2. FSM (Finite State Machine) models
3. Editing specification models with GraphWalker Studio
4. Generate simple test sequences with…
   • GraphWalker Studio and
   • Model >> Test >> Relax

Degree of automization

graph TD
    classDef sub opacity:0
    classDef note fill:#ffd, stroke:#ccb
    
     A(Degree of automatization) --> B(from the view of test execution) --> C(Manual / Automated)
  A --> D(from the view of the test design) --> E(Manually designed) --> F(Generated)
       
    subgraph subE [" "]
        E
        noteE[ Test cases are designed by a test engineer based on specification]
    end

    subgraph subF [" "]
        F
        noteF[ Test cases are generated automatically from a test model or from the specification -> MBT Model Based Testing]
    end
    
    class subA,subB,subC sub
    class noteA,noteB,noteC note

Model based testing

Conformance testing

• Given
  • Specification model (white box)
  • Implementation model (black box)
• Test if the implementation conforms to the specification?
  • I.E. determine if the two corresponding model descriptions are equivalent

graph TD
    classDef sub opacity:0
    classDef note fill:#ffd, stroke:#ccb
    
     A <--> B --> C
     B --> D 

    subgraph subA [" "]
        A
        noteE[Specification model]
    end

    subgraph subB [" "]
        B
        noteF[Implementation model]
    end

FSM (Formal specification model)

FSM-based conformance testing

graph TD
    classDef sub opacity:0
    classDef note fill:#ffd, stroke:#ccb
    
     A(Specification: FSM white box) <--> B(Implementation: FSM Impl)

graph TD
    classDef sub opacity:0
    classDef note fill:#ffd, stroke:#ccb
    
     A(Requirements) --> B(Specification FSM M) --> C(Implementation FSM M, SUT)
     B --> D[ Test suite: test case 1, ..., test case n]

graph TD
    classDef sub opacity:0
    classDef note fill:#ffd, stroke:#ccb
    
     A[Test suite] -->|Input| B(Implementation FSM Impl, SUT) -->|Observed output| C(Tester)
     A -->|Expected output| C
     C --> D{Verdict}
     

FSM exercise

Marklin Battery-Operated Signal 1.

1. Explore the functionality of the given device and write a specification for it

• The device has 2 LEDs (red and green), a 2-way switch and a press button
• The 2-way switch turns the device off or on. When the device is turned on, the green LED lights up.
• The button can be used to change which LED lights; red or green.
• If no button is pressed for 7 secs the device changes the lights.

2. Create FSM based on the specification

• Create state transition table
• Create state transition graph

3. Design an input/output sequence to test all functionalities of the specification

Waiting for 7 seconds can be handled as special timeout input message

FSM exercise - solution graph

Figure 1: State transition graph

FSM exercise - state transition table

	Switch on	Switch off	press button	wait for 7 secs
s_off	s_green/green	_	_	_
s_green	_	s_off/_	s_red/red	s_red/red
s_red	_	s_off/_	s_green/green	s_green/green

FSM exercise - solution example test sequence

Action (input)	Desired output
switch on	green
wait for 7 secs	red
wait for 7 secs	green
press button	red
switch off	_
switch on	green
press button	red
press button	green
switch off	_

Graphwalker

• Open source, free MBT tool with GUI
• Easy-to-use
• Good documentation

Working process

1. Creating a model
2. Write adaptation code that interacts with the SUT
3. Generate tests
4. Executing tests

Graphwalker Studio - Installation and start

1. Fetch the docker image by running docker pull graphwalker/studio
2. Run the image docker run -ti --rm -e DISPLAY -v /tmp/.X11-unix:/tmp/.X11-unix -v $HOME/.Xauthority:/home/developer/.Xauthority --net=host --pid=host --ipc=host graphwalker/studio

Graphwalker Studio - Alternative installation and start

If the previous approach didn’t work one can do the following steps

1. Download and install Java JDK

• Set JAVA_HOME variable in the system env list if not set auatomatically

2. Install model editor Graphwalker studio

After installation

1. Click on graphwalker studio graphwalker-studio-4.3.2.jar
2. Open a web browser and type http://localhost:9090/studio.html

Graphwalker Studio - Battery operated signal example