Question

I have two objects in my unit test, the actual and expected object. All properties on the object method are the exact same and if I run the following test:

Assert.AreEqual( expectedObject.Property1, actualObject.Property1);

the result passes as expected. However, when I try to run the following test it fails:

Assert.AreEqual (expectedObject, actualObject);

What am I missing? Can two objects not be compared and do I have to do a check on each property?

Answer 1

You need to override Equals for your object. Assert uses Object.Equals. By default, Object.Equals on objects of reference type performs a reference comparison. That is, two instances of a reference type are equal if and only if they refer to the same object. You want to override this so that instead of a reference comparison being performed a value comparison is performed. Here is a very nice MSDN article on the subject. Note that you also need to override GetHashCode. See MSDN fo the guidelines. Here is a simple example:

Before:

class Test {
    public int Value { get; set; }
}

Test first = new Test { Value = 17 };
Test second = new Test { Value = 17 };
Console.WriteLine(first.Equals(second)); // false

After:

class Test {
    public int Value { get; set; }
    public override bool Equals(object obj) {
        Test other = obj as Test;
        if(other == null) {
            return false; 
        }
        return this.Value == other.Value;
    }
    public override int GetHashCode() { 
        return this.Value.GetHashCode();
    }
}

Test first = new Test { Value = 17 };
Test second = new Test { Value = 17 };
Console.WriteLine(first.Equals(second)); // true