Unit testing that events are raised in C# (in order)

Question

I have some code that raises PropertyChanged events and I would like to be able to unit test that the events are being raised correctly.

The code that i

Answer 1

Don't write a test for each member - this is much work

(maybe this solution is not perfect for every situation - but it shows a possible way. You might need to adapt it for your use case)

It's possible to use reflection in a library to test if your members are all responding to your property changed event correctly:

• PropertyChanged event is raised on setter access
• Event is raised correct (name of property equals argument of raised event)

The following code can be used as a library and shows how to test the following generic class

using System.ComponentModel;
using System.Linq;

/// 

/// Check if every property respons to INotifyPropertyChanged with the correct property name
/// 
public static class NotificationTester
    {
        public static object GetPropertyValue(object src, string propName)
        {
            return src.GetType().GetProperty(propName).GetValue(src, null);
        }

        public static bool Verify(T inputClass) where T : INotifyPropertyChanged
        {
            var properties = inputClass.GetType().GetProperties().Where(x => x.CanWrite);
            var index = 0;

            var matchedName = 0;
            inputClass.PropertyChanged += (o, e) =>
            {
                if (properties.ElementAt(index).Name == e.PropertyName)
                {
                    matchedName++;
                }

                index++;
            };

            foreach (var item in properties)
            { 
                // use setter of property
                item.SetValue(inputClass, GetPropertyValue(inputClass, item.Name));
            }

            return matchedName == properties.Count();
        }
    }

The tests of your class can now be written as. (maybe you want to split the test into "event is there" and "event raised with correct name" - you can do this yourself)

[TestMethod]
public void EveryWriteablePropertyImplementsINotifyPropertyChangedCorrect()
{
    var viewModel = new TestMyClassWithINotifyPropertyChangedInterface();
    Assert.AreEqual(true, NotificationTester.Verify(viewModel));
}

Class

using System.ComponentModel;

public class TestMyClassWithINotifyPropertyChangedInterface : INotifyPropertyChanged
{
        public event PropertyChangedEventHandler PropertyChanged;

        protected void NotifyPropertyChanged(string name)
        {
            if (PropertyChanged != null)
            {
                PropertyChanged(this, new PropertyChangedEventArgs(name));
            }
        }

        private int id;

        public int Id
        {
            get { return id; }
            set { id = value;
                NotifyPropertyChanged("Id");
            }
        }
}