Some more on Pex

So I've been playing with Pex and I decided to try it on another application I am playing with Prism.

I had a look at the ListDictionaryFixture in the Prism.Tests project. And I set my eyes on these three TestMethods and decided to see how Pex could work here.

   1: [ExpectedException(typeof(ArgumentNullException))]

   2: [TestMethod]

   3: public void AddThrowsIfKeyNull()

   4: {

   5:     list.Add(null, new object());

   6: }


   8: [ExpectedException(typeof(ArgumentNullException))]

   9: [TestMethod]

  10: public void AddThrowsIfValueNull()

  11: {

  12:     list.Add("", null);

  13: }


  15: [TestMethod]

  16: public void CanAddValue()

  17: {

  18:     object value1 = new object();

  19:     object value2 = new object();


  21:     list.Add("foo", value1);

  22:     list.Add("foo", value2);


  24:     Assert.AreEqual(2, list["foo"].Count);

  25:     Assert.AreSame(value1, list["foo"][0]);

  26:     Assert.AreSame(value2, list["foo"][1]);

  27: }


So first I referenced the Microsoft.Pex.Framework Assembly.  Then I created a parameterized PexMethod.

   1: [PexMethod]

   2: public void TestCanAddValue(string key, object value)

   3: {

   4:     list.Add(key, value);

   5: }


And then I ran Pex.

My first result was not quite what I expected:


I would have expected at least three tests to be run by Pex, so first I check the Uninstrumented Method.


If you right-click and select Instrument assembly Pex goes and adds a PexAssemblyInfo.cs file to your project


and places the following inside the file:

   1: using Microsoft.Pex.Framework.Instrumentation;

   2: using System;

   3: using Microsoft.Pex.Framework.Validation;


   5: [assembly: PexInstrumentAssembly("Prism")]

Right, so let's run Pex again.  After Pex has run it shows me the following result:


This is what I expected.  Now I want to fix the failed Run 1 and 2.  If you look at the generated test you see that it does not say what the ExpectedException should be:

   1: [TestMethod]

   2: [PexRaisedException(typeof(ArgumentNullException))]

   3: [PexGeneratedBy(typeof(ListDictionaryFixture))]

   4: public void TestCanAddValueStringObject_20080604_155328_000()

   5: {

   6:     this.TestCanAddValue((string)null, (object)null);

   7: }


   9: [TestMethod]

  10: [PexRaisedException(typeof(ArgumentNullException))]

  11: [PexGeneratedBy(typeof(ListDictionaryFixture))]

  12: public void TestCanAddValueStringObject_20080604_155926_001()

  13: {

  14:     this.TestCanAddValue("", (object)null);

  15: }

To get Pex to generate the tests correctly you need to either Fix It or Allow It by right clicking on the row:



I chose to Allow It and then it adds another entry into the PexAssemblyInfo.cs file.

And then I reran Pex, and there you go I replaced three Unit Tests with one PexMethod.



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