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Property-Based Testing for Services
in Scala
StrangeLoop, 24 September 2015
@jessitron
Property-Based Testing
for Services
in Scala
vs example tests
Property-Based Testing
for Services
in Scala
vs example tests
not only mathy things
& Scalacheck
why are we here?
Testing
why are we here?
Go faster! Don't break things!
why do we test?
why do we test?
confidence that it works
define "it works"
drive good design
confidence that it works
define "it works"
drive good design
How do we know it?
What do we know?
what will we do today?
what will we do today?
Learn prerequisites
See the application under test
Write a test together
input
outputoutput
example tests
side effects
example tests
input
outputoutput
example tests
input
outputoutput
input
outputoutput
input
outputoutput
input
output
output
generate input
run
repe
ated
ly
track failures
narrow down cause
group properties together
generate input
run
repe
ated
ly
track failures
narrow down cause
group properties together
Scalacheck (or Scalatest)
scalacheck.Gen
PropShrink
val house = Item("house")
case class Item(name : String)
listOfItems.map { item => item.name } item.name
listOfItems.map { item => item.name }
listOfItems.map { item => item.name }
listOfItems.map { item => item.name }
listOfItems.map(item => item.name)listOfItems.map(item => item.name)
listOfItems.map( _.name )
listOfItems.map { item => item.name }
listOfItems.map(item => item.name)
listOfItems.map { item => item.name }
listOfItems.map { item => item.name }
for { item <- listOfItems } yield item.name
listOfItems.map { item => item.name }
for { item <- listOfItems } yield item.name
for-comprehension
for { item <- listOfItems } yield item.name
List[Item]
List[String]
for { item <- } yield item.name
itemGenerator
Gen[Item]
Gen[String]
for { item <- } yield item.name
itemGenerator
Gen[Item]
Gen[LineItem]
for { item <- itemGenerator price <- priceGenerator } yield LineItem(item, price)
Gen[Price]
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