Test First Programming with Microsoft 'NET

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Test First Programming with Microsoft .NET

• Benjamin Mitchell
• Consultant
• Axxiant

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Demo

• Test
• public void StartPresentationWithJoke
• Audience myAudience new Audience()
• Presentation talk new Presentation(
  myAudience, MS Soho)
• talk.Start()
• talk.TellJoke()
• Assert(Audience shouldve laughed,
  talk.AudienceResponse laugh)

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Whats the big deal?

• Finding bugs early and fixing them is critical to
  good development
• When youve written new code
• How do you know it works?
• When you have to make a change
• Will it cause new problems?
• Will old bugs rise from the grave?
• Testing first is the key

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That sounds like a good idea but

• Testing is a Good Thing but isnt always done
• Too difficult to set it up
• Thats what testers are there for
• It stops me from doing more interesting work

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Whats different now?

• Always writing the test before the code
• Too hard to add testing on later
• More interesting more likely to be done
• Use a standard test frameworks
• Freely available
• Lots of community support

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Start with the test

• Forces thinking about what the method does
• Provides an easy starting point
• Provides a finishing line
• Youre done when the test succeeds

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What are the steps?

• Design some minor functionality
• Write a test that fails
• Add the smallest amount of code to make it pass
• GoTo 1
• When all test pass release the software

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NUnit

• Written in C can be used by VB.NET or C
• Based on the JUnit implementation
• Be like Microsoft steal from Sun
• Uses attributes for tests
• Standalone application, or Visual Studio Addin

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Lets take the car for a ride!
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NUnit testing methods

• Attributes
• TestFixture
• Test
• Setup
• Teardown
• ExpectedException
• Ignore

• Methods
• Assert (bool)
• AssertEquals
• AssertNull
• AssertNotNull
• Fail

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Other benefits

• Faster to develop
• Consistent steady enhancements
• Avoids Dreaded Day Of Debugging
• Design improves
• Requirements are nailed down early
• Tests are the first users of code
• Better feedback from experience
• Creating the test can be harder than the code
• Tests document the code
• Others can see how the code should behave
• Tests can be run by anyone

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More Benefits

• No more regression testing
• Tests are part of the process
• Write once, run again and again
• Extra confidence
• Easier to get started
• The end of hope as a strategy
• Develop with less stress and anxiety
• Easier to make changes and see their impact
• Better able to handle customer changes

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Mock Objects

• Mock Objects are a good idea when the real object
  is
• Random
• Difficult to setup
• Has behaviour that is hard to trigger
• Is slow
• Has a user interface
• Test needs to check how the object was used
• Does not yet exist

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Tests go with together with Refactoring

• Keep the behaviour the same, change the
  implementation
• Avoids the evils of early optimisation
• Evolve without having to guess up front

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Go for the Green Bar

• Get there every 2 10 minutes
• Think about the quickest way of getting a green
  bar
• do the simplest thing first
• You arent going to need it
• Only 10 of that extra stuff will ever get used,
  so you are wasting 90 of your time.

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Doing it

• It may be slower to begin with
• Best with component-based systems
• More difficult with UI and web pages
• Can and has been done successfully
• Requires a different design
• MockObjects frameworks exist for n-tier database
  developments

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How to write good tests

• Must be small, simple and fast to run
• Focus on
• Things that will change or might fail
• Tests that take a few minutes to write
• Manual tasks that need to be done more than once
• Each Bug deserves its own test
• Write a test that fails first
• Then fix the bug
• Repeat bugs become Shootable Offences
• Avoid large Scenarios Keep tests independent

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Where can I find out more?

• At the pub!
• Extreme Tuesday Club meets every Tuesday at The
  Old Bank Of England!
• Attendees this year include Martin Fowler
  (Refactoring) and Alistair Cockburn (Agile
  Methodologies) plus the creators of Mock Objects
• http//www.xpdeveloper.com/

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Get going

• http//www.nunit.org/
• Starting takes around an hour
• Become Test Infected
• Never write a line of functional code without a
  broken test case Kent Beck

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