BabyMock is a visual mock object library for Pharo Smalltalk, that supports test-driven development. http://youtu.be/xChlI4j4Euc

1. Test-driven development in
with BabyMock 2
Attila Magyar
FOSDEM 01/02/2014
Brussels

2. Who am I?
Attila Magyar
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Java for living
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Smalltalk for joy, since 2012
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Python, Groovy, Lisp, etc..
TDD for about 4 years
Contact:
http://twitter.com/zeroflag

3. Agenda
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About TDD and Mock objects in general
About BabyMock 2
● Differences between the new and the old version
● How does it work?
● Few words about the internals
DEMO

4. Outside-in TDD with Mocks
B
3
age
ss
Me
Message 2
A
Me
ssa
ge
4
R
es
po
ns
e
Test
Message 1
C

5. Expect Message 3
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Exactly once
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With x argument
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Outside-in TDD with Mocks
MOCK B
3
age
ss
Me
Message 2
Allow Message 4
● Any number of times
● With y argument
● Answer „Response”
A
●
Me
ssa
ge
4
R
es
po
ns
e
Test
Message 1
Inter-object protocol
MOCK C

6. BabyMock is a visual mock object library
http://smalltalkhub.com/#!/~zeroflag/BabyMock2/
Get a good mental picture of the objects relationships, and
the inter-object protocol
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Identifying test failures is easier

7. The old syntax (BabyMock 1)

8. The new syntax (BabyMock 2)

9. Expectations
Under the hood

10. How does it work?
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Mock object is a Proxy that intercepts all messages
Using the doesNotUnderstand is easiest way to implement it
(but limited).
Nil methodDictionary + cannotInterpret
More information:
Efficient Proxies in Smalltalk by Mariano Martinez Peck et al.

11. BabyMock visualized with BabyMock

12. BabyMock visualized with BabyMock

13. BabyMock visualized with BabyMock

14. DEMO
ShoppingCart
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Adding new item ids
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CreditCard
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Paying for its content
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PriceCatalog

15. Food for thought
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http://jmock.org/
(https://github.com/jmock-developers/jmock-library)
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Evolving an Embedded Domain-Specific Language in Java, Freeman, S. and Pryce, N.
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Mock Roles, Not Objects. OOPSLA 2004, Freeman, S., Mackinnon, T., Pryce, N., Walnes, J.,
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Growing Object-Oriented Software, Guided by Tests, Freeman, S. and Pryce, N.
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Efficient Proxies in Smalltalk, Mariano Martinez Peck et al.