In the previous post, we went through the exploration testing process to exercise a simple method, CheckPositive. In this post, we'll try the same exploration testing, but will let Pex do it.

// mehod under test
1 void CheckPositive(int i, bool @throw) {
2     if (i < 0) {      
3          Console.WriteLine("not ok");
4          if (@throw)
5             throw new ArgumentException();
6     }
7     else
8         Console.WriteLine("ok");
9 }
// hand-crafted unit tests
[TestMethod] void Zero() {
     CheckPositive(0, false);
}
[TestMethod] void MinusOne() {
     CheckPositive(-1, false);
}
[TestMethod] void MinusOneAndThrow() {
     CheckPositive(-1, true);
}

Exploration testing with Pex

To let Pex explore the CheckPositive, we write a little test wrapper around that method:

[TestClass, PexClass]
public partial class ExplorationTesting {
    [PexMethod]
    public void Test(int i, bool @throw) {
        CheckPositive(i, @throw);
    }

We also instrumented the original method with additional methods to track down the path conditions that Pex computes along the execution traces. Pex generates 3 pairs of values which are equivalent to what the test we manually created:

• 0, false
• int.MinValue, false
• int.MinValue, true (throws)