The document discusses FlexMock and Mocha, two Ruby libraries for mocking objects in tests. It describes what mocks are and when they should be used. It then outlines a "mockfight" between FlexMock and Mocha, where different testing scenarios are tried with each library. Both libraries are able to handle the scenarios. In the end, the document concludes that the two libraries now have similar features and the choice between them comes down to personal preference of syntax.

1. Mockfight!
FlexMock vs. Mocha
Patrick Reagan
patrick@viget.com
Director, Application Development
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

2. Mockfight! FlexMock vs. Mocha 2
What are Mocks?
“Mock objects are simulated
objects that mimic the behavior of
real objects in controlled ways”
- Wikipedia
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3. Mockfight! FlexMock vs. Mocha 3
When to Mock?
Use mocks when you want to:
• Control the behavior of internal method calls
• Remove dependence on external systems
• Improve test performance
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

4. Mockfight! FlexMock vs. Mocha 4
Control Behavior
What does this return?
Need to maintain consistency between calls
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

5. Mockfight! FlexMock vs. Mocha 5
Control Behavior
How do we test?
Magic happens
here
Stub the call to Die#rand (using Mocha)
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6. Mockfight! FlexMock vs. Mocha 6
Remove Dependencies
Example: retrieve response data via HTTP
To test this, we need to mock:
• Call to URI#parse
• Calls to Net::HTTP#new and Net::HTTP#head
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

7. Mockfight! FlexMock vs. Mocha 7
Mockfight!
Expanded example:
• Create class method to check for resource
• Handle errors and redirects
• Iteratively develop functionality while testing
• Examine the differences between libraries
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8. Mockfight! FlexMock vs. Mocha 8
Round 1
Test scenario when URI#parse raises exception
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9. Mockfight! FlexMock vs. Mocha 9
Round 1: Results
FlexMock
Mocha
Viget Labs
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

10. Mockfight! FlexMock vs. Mocha 10
Round 2
Check for a valid response
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11. Mockfight! FlexMock vs. Mocha 11
Round 2: Results
FlexMock
Mocha
Viget Labs
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

12. Mockfight! FlexMock vs. Mocha 12
Round 3
Check for response type instead of status code
* Our previous tests for response status code are now invalid
Viget Labs
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

13. Mockfight! FlexMock vs. Mocha 13
Round 3: Results
FlexMock
Mocha
Viget Labs
we build web business
July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

14. Mockfight! FlexMock vs. Mocha 14
Round 4
Follow an HTTP redirect response
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15. Mockfight! FlexMock vs. Mocha 15
Round 4: Results
FlexMock
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16. Mockfight! FlexMock vs. Mocha 16
Round 4: Results
Mocha
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

17. Mockfight! FlexMock vs. Mocha 17
Round 5
Handling maximum number of redirects
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

18. Mockfight! FlexMock vs. Mocha 18
Round 5: Results
FlexMock
Viget Labs
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

19. Mockfight! FlexMock vs. Mocha 19
Round 5: Results
Mocha
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20. Mockfight! FlexMock vs. Mocha 20
Bonus Round
Mocking ActiveRecord#find in controllers
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21. Mockfight! FlexMock vs. Mocha 21
Bonus Round: Results
FlexMock
Mocha
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22. Mockfight! FlexMock vs. Mocha 22
But Wait, There’s More
Mocha has parameter matchers (in SVN)
You can write code like this:
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23. Mockfight! FlexMock vs. Mocha 23
Conclusion
• Newest versions of gems contain similar features
• FlexMock can accept blocks for further mocking
• Personal preference of syntax is the deciding factor
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

24. Mockfight! FlexMock vs. Mocha 24
It’s a Tie!
Ultimately, two great libraries - just pick one
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July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

25. Mockfight! FlexMock vs. Mocha 25
Questions?
???
Viget Labs
we build web business
July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com

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Additional Information
FlexMock (Jim Weirich)
http://www.onestepback.org/software/flexmock
Mocha (James Mead)
http://mocha.rubyforge.org
http://www.slideshare.net/viget
Viget Labs
we build web business
July 18, 2007 © Copyright 2007 Viget Labs, LLC – www.viget.com