ScalaCheck

Presented at Scaladores, August/2013

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