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Test Driven DevelopmentImproving .NET Application Performance & Scalability

Brendon Birdoes(brendon.birdoes@neudesic.c

om)

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Agenda• Challenges we deal with today• Be Agile - Test Driven Development• Code coverage• Database can be Unit Tested!• Benefits of TDD• Summary• Q&A

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Challenges we deal with today

• Does our code do what we intended?• Documentation – is it updated?• Debug – again?• Change Request – What did I break?

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Get Agile – Test Driven Development

Tools For Agility, Kent Beck

Practices

Tools

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Unit Test Defined• Code programmers write to exercise

each method in the design that run quickly and help localize errors – Isolates and tests a single operation– Run in any environment– Less time debugging– Side affect is documentation!

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Unit Tests Defined• Tests are NOT unit tests when

they…– Talk to a database– Communicate across the network– Touch the file system– Require human intervention (such as

modifying a *.config file, starting a console app, etc.) to run

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What is Test Driven Development?

• Despite the name, TDD focuses on “Design” first, “Test” second

• Basic tenants are:–Write a failing automated test before

you write any code• Focus on interface and use case or problem• Tests get written• Just enough code to pass the test

– Remove duplication (refactor)

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Test Driven DevelopmentThe motto "Red, Green,

Refactor ".

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demoDeveloper Unit Test

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Code Coverage Defined• Also known as “test coverage”• It measures how thoroughly the

automated tests exercise the production code, its source code statements, branches, and expressions

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What degree of code coverage should you aim for?

• Answer: It depends• Average code coverage is around

85%• Biggest blocker to attain 100% -

existing code, auto generated code• Aim for 100% while learning – you’ll

understand why 85% is nicer

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demoCode Coverage

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Database can be Unit Tested!

User Interface

ApplicationCode

UnitTestsData Access

Layer

Stored Procedures

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demoDatabase Unit Test

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TDD in Action: Active BugBug: Expired Credit Cards are being

Credited

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Quality Indicators

Iteration 1 Iteration 3 Iteration 4 Iteration 5Iteration 2

91

20

51

76

60

56

19

18

40

71

80

32.5

12

8

9

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Traditional testing

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Test Driven Development

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TDD - Application Lifecycle

Development Testing & Bug Fixing UATDevelopment

Testing & Bug

FixingUAT

Development and testing/bug fixing take about the same amount of time Development takes more time than testing, and testing time is reduced

Overall lifecycle is shortened

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Unit testing is a learned skill that can only be honed with

experience.

Interfaces

Mock Objects

Better Factored Code

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Starting Test Driven Development

Creating a cultural change is hard…

….. and it can be done.

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Summary• Development becomes more

challenging.• TDD is a great tool to overcome these

challenges• Database can be Unit Tested!• Development is Faster using TDD.• VSTS is a great tool for UT and TDD.

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Q & A

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