The document summarizes a presentation given at the ACM SIGPLAN Erlang Workshop in 2016 about automatically generating UML sequence diagrams from QuickCheck test counterexamples in Erlang. It discusses the challenges of interpreting counterexamples to find bugs, presents an example of a failing phone exchange test case, and shows how the counterexample could be shrunk and represented as a UML sequence diagram. Future work ideas are also proposed, like handling components and state diagrams.

1. Automatic Generation
of UML Sequence Diagrams
from Test Counterexamples
Daniel Carballa1
, Laura M. Castro1
1Universidade da Coruña (Spain)
ACM SIGPLAN Erlang Workshop
Nara, 23th September 2016
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15. Erlang ecosystem
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16. Erlang ecosystem
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17. Testing with QuickCheck
It’s so great!
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18. Testing with QuickCheck
It’s so great... when everything works! :)
> eqc:quickcheck(eqc:testing_time(5,module:property())).
...............................................................................
.....................(x10).....................................................
...............................................(x100)..........................
.......................................................................(x1000).
...............................................................................
....................(x10000)...................................................
.............................................(x1000).....(x100)......(x1)..
Time limit reached: 5.0 seconds.
OK, passed 1076702 tests
true
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19. Testing with QuickCheck
We know the two main challenges are:
1 Writing the right property/s and/or model/s, data generators
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20. Testing with QuickCheck
We know the two main challenges are:
1 Writing the right property/s and/or model/s, data generators
Graphical editing of models
Automatic inference of data generators
Translation of properties and models into semi-natural language
ACM SIGPLAN Erlang Workshop (2016) QC to UML 17 / 27

21. Testing with QuickCheck
We know the two main challenges are:
1 Writing the right property/s and/or model/s, data generators
Graphical editing of models
Automatic inference of data generators
Translation of properties and models into semi-natural language
2 Fixing the bug(s)!
ACM SIGPLAN Erlang Workshop (2016) QC to UML 17 / 27

22. Testing with QuickCheck
We know the two main challenges are:
1 Writing the right property/s and/or model/s, data generators
Graphical editing of models
Automatic inference of data generators
Translation of properties and models into semi-natural language
2 Fixing the bug(s)! (i.e. interpreting counterexamples)
ACM SIGPLAN Erlang Workshop (2016) QC to UML 17 / 27

23. Testing with QuickCheck
We know the two main challenges are:
1 Writing the right property/s and/or model/s, data generators
Graphical editing of models
Automatic inference of data generators
Translation of properties and models into semi-natural language
2 Fixing the bug(s)! (i.e. interpreting counterexamples)
Shrinking!!
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24. Example: phone exchange
start() -> ok
activate(PhoneNumber) -> ok
deactivate(PhoneNumber) -> ok
call(CallerPhoneNumber,CalleePhoneNumber) -> ok
list() -> {ok,[PhoneNumbers]}
nsa() -> {ok,[OnGoingPhoneCalls]}
stop() -> ok
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25. Example: phone exchange
start() -> ok
activate(PhoneNumber) -> ok
deactivate(PhoneNumber) -> ok
call(CallerPhoneNumber,CalleePhoneNumber) -> ok
list() -> {ok,[PhoneNumbers]}
nsa() -> {ok,[OnGoingPhoneCalls]}
stop() -> ok
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26. Interpreting counterexamples
eqc:quickcheck(eqc:numtests(200,centralita_statem:prop_centralita())).
...........................................................................................
.........(x10).(x1).........Failed! After 120 tests.
[{set,{var,1},{call,centralita,start,[]}},
{set,{var,2},{call,centralita,activate,[-24]}},
{set,{var,3},{call,centralita,deactivate,[9]}},
{set,{var,4},{call,centralita,list,[]}},
{set,{var,5},{call,centralita,nsa,[]}},
{set,{var,6},{call,centralita,nsa,[]}},
{set,{var,7},{call,centralita,activate,[-24]}},
{set,{var,8},{call,centralita,activate,[20]}},
{set,{var,9},{call,centralita,activate,[38]}},
{set,{var,10},{call,centralita,call,[-24,20]}},
{set,{var,11},{call,centralita,list,[]}},
{set,{var,12},{call,centralita,activate,[-27]}},
{set,{var,13},{call,centralita,list,[]}},
{set,{var,14},{call,centralita,nsa,[]}},
{set,{var,15},{call,centralita,call,[38,20]}}]
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27. Interpreting counterexamples
centralita:start() -> ok
centralita:activate(-24) -> ok
centralita:deactivate(9) -> ok
centralita:list() -> {ok, [-24]}
centralita:nsa() -> {ok, []}
centralita:nsa() -> {ok, []}
centralita:activate(-24) -> ok
centralita:activate(20) -> ok
centralita:activate(38) -> ok
centralita:call(-24, 20) -> ok
centralita:list() -> {ok, [38, 20, -24]}
centralita:activate(-27) -> ok
centralita:list() -> {ok, [-27, 38, 20, -24]}
centralita:nsa() -> {ok, [[]]}
Reason:
Post-condition failed:
false
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28. Interpreting counterexamples
Shrinking
Shrinking xxxxxxxx..x.x..xx..xxxxxxxxxx(7 times)
[{set,{var,1},{call,centralita,start,[]}},
{set,{var,2},{call,centralita,activate,[-24]}},
{set,{var,3},{call,centralita,activate,[20]}},
{set,{var,4},{call,centralita,call,[-24,20]}},
{set,{var,5},{call,centralita,nsa,[]}}]
centralita:start() -> ok
centralita:activate(-24) -> ok
centralita:activate(20) -> ok
centralita:call(-24, 20) -> ok
centralita:nsa() -> {ok, [[]]}
Reason:
Post-condition failed:
false
false
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29. Interpreting counterexamples
Graphical representation
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30. From counterexamples to UML sequences
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31. Future ideas
Test it with really long failing sequences
(send us your counterexamples!!)
Test it with components, mocks, etc.
Combine info from QC with EVM traces so that UML contains
more info of what happens “behind the scenes”
Translate PlantUML state diagrams into stateful test models
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32. Questions?
Tool and samples available at: BitBucket git repo.
Extended version of paper: ask me!
Audience ! thanks
@lauramcastro
lcastro@udc.es
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33. Credits
Image authoring attribution (in order of appearance)
‘Senior couple having fun’, by Be-Younger.com.
‘Nikola Tesla with his equipment’, by Dickenson V. Alley.
‘Pizza guy’, by Nico Kaiser.
‘Servicemen repairing buses in Ubon’, by Ilya Plekhanov.
‘Is lucid dreaming actually real?’, by HowToLucid.com.
‘The Almost Useless Machine’, by tinkerlog.
‘Sailors practice repairing leaks’, by US Navy.
‘Gollum close up’, by mellisea.
‘Blue screen at Portal’s presentation during Game Developers Conference 2010’, by Official GDC.
‘Lilly’s crying’, by Green Smoothies Rock!
‘Child receives ear exam’, by World Bank Photo Collection.
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