The document discusses test-driven development (TDD) and the Babymock 2 library, highlighting key differences from its predecessor and its functionality in facilitating TDD with mock objects. It covers the internal workings of Babymock, offering insights into its syntax, expectations, and the benefits of visualizing inter-object relationships. The document also provides links to resources for further exploration of TDD and mock objects.

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.