ScalaCheck

E54f4140dc133a17200fe7a104c33a8e?s=47 Pedro Matiello
August 28, 2013
Programming
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260

 ScalaCheck

Presented at Scaladores, August/2013

E54f4140dc133a17200fe7a104c33a8e?s=128

Pedro Matiello

August 28, 2013
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Transcript

  1. SCALACHECK

  2. SCALACHECK Pedro Matiello pedro@pmatiello.me @pmatiello

  3. SCALACHECK • Property-based testing • Scala

  4. PROPERTIES

  5. PROPERTIES def sum(x:Int, y:Int) = x + y

  6. PROPERTIES def sum(x:Int, y:Int) = x + y # Property:

    ∀x,y : sum(x,y) = sum(y,x)

  7. PROPERTIES def sum(x:Int, y:Int) = x + y # Property:

    ∀x,y : sum(x,y) = sum(y,x) val commutativity = forAll { (x:Int, y:Int) => sum(x,y) == sum(y,x) }

  8. PROPERTIES def sum(x:Int, y:Int) = x + y # Property:

    ∀x,y : sum(x,y) = sum(y,x) val commutativity = forAll { (x:Int, y:Int) => sum(x,y) == sum(y,x) }

  9. PROPERTIES def sum(x:Int, y:Int) = x + y # Property:

    ∀x,y : sum(x,y) = sum(y,x) val commutativity = forAll { (x:Int, y:Int) => sum(x,y) == sum(y,x) } org.scalacheck.Prop.forAll

  10. PROPERTIES def sum(x:Int, y:Int) = x + y # Property:

    ∀x,y : sum(x,y) = sum(y,x) val commutativity = forAll { (x:Int, y:Int) => sum(x,y) == sum(y,x) } commutativity.check

  11. PROPERTIES def sum(x:Int, y:Int) = x + y # Property:

    ∀x,y : sum(x,y) = sum(y,x) val commutativity = forAll { (x:Int, y:Int) => sum(x,y) == sum(y,x) } commutativity.check + OK, passed 100 tests

  12. CONDITIONAL PROPERTIES

  13. CONDITIONAL PROPERTIES def sum(x:Int, y:Int) = x + y #

    Property: ∀x,y>0 : sum(x,y) > x

  14. CONDITIONAL PROPERTIES def sum(x:Int, y:Int) = x + y #

    Property: ∀x,y>0 : sum(x,y) > x val greater = forAll { (x:Int, y:Int) => y > 0 ==> sum(x,y) > x }

  15. CONDITIONAL PROPERTIES def sum(x:Int, y:Int) = x + y #

    Property: ∀x,y>0 : sum(x,y) > x val greater = forAll { (x:Int, y:Int) => y > 0 ==> sum(x,y) > x }

  16. CONDITIONAL PROPERTIES def sum(x:Int, y:Int) = x + y #

    Property: ∀x,y>0 : sum(x,y) > x val greater = forAll { (x:Int, y:Int) => y > 0 ==> sum(x,y) > x } greater.check

  17. CONDITIONAL PROPERTIES def sum(x:Int, y:Int) = x + y #

    Property: ∀x,y>0 : sum(x,y) > x val greater = forAll { (x:Int, y:Int) => y > 0 ==> sum(x,y) > x } greater.check ! Falsified after 2 passed tests. > ARG_0: 51047075 > ARG_1: 2096436573

  18. CONDITIONAL PROPERTIES scala> 51047075 + 2096436573 res0: Int = -2147483648

  19. CONDITIONAL PROPERTIES scala> 51047075 + 2096436573 res0: Int = -2147483648

    scala> 51047075l + 2096436573l res1: Long = 2147483648

  20. GENERATORS

  21. GENERATORS def sum(x:Int, y:Int) = x + y # ∀x,y,

    x%2=0,y%2=0 : sum(x,y)%2 = 0

  22. GENERATORS def sum(x:Int, y:Int) = x + y # ∀x,y,

    x%2=0,y%2=0 : sum(x,y)%2 = 0 val evenInt = arbitrary[Int] suchThat (_ % 2 == 0)

  23. GENERATORS def sum(x:Int, y:Int) = x + y # ∀x,y,

    x%2=0,y%2=0 : sum(x,y)%2 = 0 val evenInt = arbitrary[Int] suchThat (_ % 2 == 0) org.scalacheck.Arbitrary.arbitrary

  24. GENERATORS def sum(x:Int, y:Int) = x + y # ∀x,y,

    x%2=0,y%2=0 : sum(x,y)%2 = 0 val evenInt = arbitrary[Int] suchThat (_ % 2 == 0) forAll(evenInt, evenInt) { (x:Int, y:Int) => sum(x,y) % 2 == 0 }.check

  25. GENERATORS def sum(x:Int, y:Int) = x + y # ∀x,y,

    x%2=0,y%2=0 : sum(x,y)%2 = 0 val evenInt = arbitrary[Int] suchThat (_ % 2 == 0) forAll(evenInt, evenInt) { (x:Int, y:Int) => sum(x,y) % 2 == 0 }.check

  26. GENERATORS def sum(x:Int, y:Int) = x + y # ∀x,y,

    x%2=0,y%2=0 : sum(x,y)%2 = 0 val evenInt = arbitrary[Int] suchThat (_ % 2 == 0) forAll(evenInt, evenInt) { (x:Int, y:Int) => sum(x,y) % 2 == 0 }.check + OK, passed 100 tests

  27. SCALACHECK Pedro Matiello pedro@pmatiello.me @pmatiello