Test Driven DevelopmentDriving Development by Tests

Haarlem Software Developer Meetup@mcbeelen

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KvK 53479335

Lichtfabriekplein 1, 2031 TE Haarlem

P.O. Box 2031 , 2002 CA Haarlem

+31 (0)88 248 1632, info@ximedes.com

www.ximedes.com

Meetup Sponsor:

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User StoryIn order to ….. achieve some goalAs a .... actorI want to ...... have certain functionality

Scenario: ExampleGiven….. some situationWhen.... perform actionThen...... verify correct behaviour

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Once upon a time …

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Controller

Validator Service

Collaborator

Converter

Acceptance Test

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Controller

Validator Service

Collaborator

Converter

Acceptance Test

UnitTest

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Controller

MockValidator

MockService

ObsoleteCollaborator

MockConverter

UnitTestLondon School of TDD

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Three options to make a test pass:

1 2

Obvious Implementation

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assertThat(calculate.multiply(2 * 5), is(10));

1 2multiply(x, y) { return x * y;}

multiply(x, y) { return 10;}

multiply(x, y) { return 2 * 5;}

multiply(x, y) { return x * y;}

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Triangulation3

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assertThat(calculate.multiply(2 * 5), is(10));3

multiply(x, y) { return 10;}

assertThat(calculate.multiply(2 * 7), is(14));

multiply(x, y) { return 2 * y;}

assertThat(calculate.multiply(3 * 7), is(21));

multiply(x, y) { return x * y;}

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Baby steps TDD

http://www.tddfellow.com/blog/2016/10/19/do-more-with-baby-steps-tdd/

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The Transformation Priority Premise

“As the tests get more specific, the code gets more generic.”

https://8thlight.com/blog/uncle-bob/2013/05/27/TheTransformationPriorityPremise.html

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1. You are here to LEARN. (and have fun)

2. Try to do your best.

3. Work in pairs.Find a partner in a similar programming language and operating system

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1 2

Primefactors:

Factorize a positive integer number into its prime factors.

Pokerhands:

Determine the winner given two pokerhands.

See you next time: March16thTest Driven Development

Refactoring Haarlem Software Developer Meetup