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1 ScalaCheck: Property-based Testing

1.1 Traditional versus property-based unit testing

import junit.framework.TestCase;

public class MathTest extends TestCase {

  public void testMax() {
    int z = Math.max(1,2)
    assertEquals(2, z)
  }

}


import junit.framework.TestCase;

public class MathTest extends TestCase {

  public void testMax2() {
    int z = Math.max(1,0)
    assertEquals(1, z)
  }

  public void testMax3() {
    int z = Math.max(10,10)
    assertEquals(10, z)
  }

  public void testMax4() {
    int z = Math.max(-2,0)
    assertEquals(0, z)
  }

}


import org.scalacheck.Properties
import org.scalacheck.Prop.forAll

object MathProps extends Properties("Math") {

  property("max") = forAll { (x: Int, y: Int) =>
    val z = java.lang.Math.max(x, y)
    (z == x || z == y) && (z >= x && z >= y)
  }

}


  

1.2 Benefits from property-based testing

  scala> p.check
  ! Falsified after 23 passed tests.
  > ARG_0: List("-1", "-1")
  > ARG_0_ORIGINAL: List("935472295", "1", "-1", "-1",
    "2147483647", "2113129492", "2147483647")

  scala> p.check
  ! Falsified after 3 passed tests.
  > ARG_0: List("1", "1")
  > ARG_0_ORIGINAL: List("0", "1", "1", "1",
    "2147483647")


  

1.3 Conclusion