intro to unit testing with test driven development
DESCRIPTION
Test Driven Development is a technique that requires Unit Tests for code to be written before the code itself. By placing the emphasis on testing, developers can define success before code is written. This helps us answer that elusive question of "when is code done?" TDD offers additional benefits such as only writing code you need to satisfy your requirements (YAGNI), and enhanced maintainability.TRANSCRIPT
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Joel Cochran
Lead Developer, WintellectNOW.com
@joelcochran
Intro to Test Driven Development (TDD)
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About Me
Microsoft Client Development MVPASPInsiderTwitter: @joelcochranEmail: [email protected]: joelcochran.comLead Developer, WintellectNOW
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About Wintellect
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COCHRAN-13
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Interview with a Method
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The Multiply Method Signature
Int32 Multiply(Int32[] values)
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Question #1
What parameter(s) do you take?
An Array of Int32
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Question #2
What value type do you return?
Int32
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Question #3
What happens when I pass you:[3, 4]?
I don’t know
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Question #4
What happens when I pass you:[7]?
I don’t know
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Question #5
What happens when I pass you:[-5, 12, 10, -3]?
I don’t know
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Question #6
What happens when I pass you:null?
I don’t know
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Question #7
What happens when I pass you:[23, Int32.MaxValue]?
I don’t know
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Question #8
You don’t seem to know much…
If you don’t know the answer to these questions, who does?
The Unit Tests
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What is a Unit Test?
Code that tests code
Small discrete chunks (units)
One test, one condition
Based on assumptions
Should be automated and repeatable
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What a Unit Test is Not
An end-to-end test
Connected to live data
Performing external functions (like sending an Email)
User tests
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Why write Unit Tests?
Test code to ensure proper functionality given certain assumptions
Exercise code without running the app
Write once, run a million times
Guards against unintended consequences
Tests define success
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What is TDD?
Unit Tests are written before the code
Helps shape the code to the task at hand
Provides focus (YAGNI)
The test defines success
Run all tests every time
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TDD Pattern
REDwrite a failing test
GREEN write enough code to
pass
REFACTORengineer the code
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Anatomy of a Unit Test
Arrange
•Assumptions•Expectations
Act•Execute•Results
Assert•Compare•Report
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TDD Kata
Daily exercise – 30 minutes or less
Roy Osherove, author of “The Art of Unit Testing”, Manning Publications
http://osherove.com/tdd-kata-1/
Let’s code!
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The String Calculator Kata
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StringCalculator Kata
