ScalaCheck

Presented at Scaladores, August/2013

Transcript

1. SCALACHECK
   

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

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3. SCALACHECK
   • Property-based testing
   • Scala
   

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4. PROPERTIES
   

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

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

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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)
   }
   

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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)
   }
   

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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
   

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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
    

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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
    

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12. CONDITIONAL PROPERTIES
    

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13. CONDITIONAL PROPERTIES
    def sum(x:Int, y:Int) = x + y
    # Property: ∀x,y>0 : sum(x,y) > x
    

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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
    }
    

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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
    }
    

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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
    

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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
    

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

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19. CONDITIONAL PROPERTIES
    scala> 51047075 + 2096436573
    res0: Int = -2147483648
    scala> 51047075l + 2096436573l
    res1: Long = 2147483648
    

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20. GENERATORS
    

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21. GENERATORS
    def sum(x:Int, y:Int) = x + y
    # ∀x,y, x%2=0,y%2=0 : sum(x,y)%2 = 0
    

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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)
    

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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
    

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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
    

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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
    

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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
    

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

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