Test Driven Development

Ben Hoskins

Test Driven Development

a.k.a.

Contract First Development

(Design by Contract (C))

a.k.a.

Behaviour Driven Development

With a little help from

Domain Driven Design

Test Driven Development

SetupExercise functionAssertTeardown

Contract First Development

Acceptable and unacceptable input valuesPreconditionsReturn valuesException that can occur, and their meaningsSide effectsPostconditionsInvariantsPerformance guarantees

Behaviour Driven Development

GivenWhenThen

Behaviour Driven Development

GivenAcceptable and unacceptable input valuesInvariantsPreconditions

WhenEvent to trigger the function under development

ThenReturn valuesException that can occur, and their meaningsSide effectsPostconditionsInvariantsPerformance guarantees

Test Driven Development

SetupGiven

Acceptable and unacceptable input valuesPreconditionsExecute function

WhenEvent to trigger the function under developmentAssert

ThenReturn values etc...Tear Down

Test Driven Development...with a little help from Domain Driven Design

@Testpublic void canCalculateASingleValue() {

Persona henry = PersonaFactory.sensibleDefaults().and("HenryHumble");String shareValue = TestConstants.SINGLE_SHARE_VALUE;ShareCalculator shareCalculator=new ShareCalculator(driver, shareValue);henry.enterShareAmountInto(shareCalculator);Assert.assertEquals("1.65", shareCalculator.getTotalValue());

}

Test Driven Development...with a little help from Domain Driven Design

@Testpublic void canCalculateASingleValue() {

Persona henry = PersonaFactory.sensibleDefaults().and("HenryHumble");String shareValue = TestConstants.SINGLE_SHARE_VALUE;ShareCalculator shareCalculator=new ShareCalculator(driver, shareValue);henry.enterShareAmountInto(shareCalculator);Assert.assertEquals("1.65", shareCalculator.getTotalValue());

}

The behaviour is:Share Calculator can calculate a single value

Test Driven Development...with a little help from Domain Driven Design

@Testpublic void canCalculateASingleValue() {

Persona henry = PersonaFactory.sensibleDefaults().and("HenryHumble");String shareValue = TestConstants.SINGLE_SHARE_VALUE;ShareCalculator shareCalculator=new ShareCalculator(driver, shareValue);henry.enterShareAmountInto(shareCalculator);Assert.assertEquals("1.65", shareCalculator.getTotalValue());

}

The setup / givens are:Henry Humble, a shareholder with 1 share,

A share value of 1.65

Test Driven Development...with a little help from Domain Driven Design

@Testpublic void canCalculateASingleValue() {

Persona henry = PersonaFactory.sensibleDefaults().and("HenryHumble");String shareValue = TestConstants.SINGLE_SHARE_VALUE;ShareCalculator shareCalculator=new ShareCalculator(driver, shareValue);henry.enterShareAmountInto(shareCalculator);Assert.assertEquals("1.65", shareCalculator.getTotalValue());

}

The execute function / when is:Henry Humble enters his share amount into

The share calculator

Test Driven Development...with a little help from Domain Driven Design

@Testpublic void canCalculateASingleValue() {

Persona henry = PersonaFactory.sensibleDefaults().and("HenryHumble");String shareValue = TestConstants.SINGLE_SHARE_VALUE;ShareCalculator shareCalculator=new ShareCalculator(driver, shareValue);henry.enterShareAmountInto(shareCalculator);Assert.assertEquals("1.65", shareCalculator.getTotalValue());

}

The assert / then is:The share calculator shows a total value of 1.65

Test Driven Development...with a little help from Domain Driven Design

In our example there domain driven design was appliedto the test:

The behaviour:A person can input their shares into the share calculator, the share calculator displays the total value of the shares.

The domain:A fixed share price,A share calculator,

can calculate a share price,has the total value available,

A Person, with a fixed amount of shares