Scrum med ITMaskinen

I fredags hade jag unge herr Deurell en föreläsning för ITMaskinen om agile, Scrum och hur man kan använda Microsofts verktyg för att lyckas. Min roll var så klart att prata om agile och Scrum och Micke pratade om TFS och vikten av test med hjälp av Team System.

Läs mer i inlägget De tre vise männen coh Scrum på ITMaskinens eminenta bloggsida.

Compare objects in unit test

Today I wanted to create some unit tests for a object relationship mapper that Connecta developed for a client. The method I wanted to test was a find method that takes an id for an entity and returns that entity from the database. The entity that I searched for was created in a static method marked with the [ClassInitialize()] attribute.

By the way, I use Team System for unit testing.

So, how do I compare the objected that I created with the object that I got from the database? Will I be happy with just comparing what ToString returns or do I take a random number of properties and compare them? No, the only reasonable thing to do is to compare the value of every property on the objects.

To do this I created a new static class in my test project called
ObjectComparer. ObjectComparer has one method called CompareObjects that takes the two objects to compare as in-parameters. Then I use reflection to find the properties on the object and compare the value of every property in the two objects. That worked really well but I soon realized that I needed a way to exclude properties from the compare method. For instance there can be a datetime field that holds a datetime for when the record was created in the database. This field will never be the same in a compare and therefore needs to be ignored. So I added another parameter that will hold a generic list that contains the names of the properties to ignore: List<string> IgnoreList.
CompareObjects returns another object called ObjectCompareResult that contains two properties, a Boolean containing the result of the compare and a string containing the possible error message if the compare returns false.

Here is the code for the method CompareObjects:

public static ObjectCompareResult CompareObjects(object obj1, object obj2, List<string> IgnoreList)
{
    Type objectType1 = obj1.GetType();
    PropertyInfo[] propertyInfos = objectType1.GetProperties();
    foreach (PropertyInfo propertyInfo in propertyInfos)
    {
        if (IgnoreList == null || (IgnoreList != null && !IgnoreList.Contains(propertyInfo.Name.ToString())))
            if (!propertyInfo.GetValue(obj1, null).Equals(propertyInfo.GetValue(obj2, null)))
                return new ObjectCompareResult(false, String.Format("The value of the property '{0}' is not the same in the two objects. Value from obj1 = '{1}'. Value from obj2 = '{2}'",
                    propertyInfo.Name.ToString(),
                    propertyInfo.GetValue(obj1, null),
                    propertyInfo.GetValue(obj2, null)));
    }
    return new ObjectCompareResult(true);
}

And here is the code for the unit test:

[TestMethod()]
public void FindTest()
{
    MyStorage target = FrameworkUnitTest.Framework_Storage_MyStorageAccessor.CreatePrivate();
    MyEntity expected = myEntity; //Created in the ClassInitialize
    MyEntity actual = target.Find(myId);
    List ignoreList = new List();
    ignoreList.Add("DateCreated");

    ObjectCompareResult result = ObjectComparer.CompareObjects(expected, actual);

    Assert.IsTrue(result.CompareResult, result.CompareMessage);
}

Thanks to my peers for help when it comes to reflection and comparing object values!