PropertyAsserts.cs

using System;
using System.ComponentModel;
using System.Diagnostics.CodeAnalysis;
using System.Threading.Tasks;
using Xunit.Sdk;

namespace Xunit
{
#if XUNIT_VISIBILITY_INTERNAL 
    internal
#else
    public
#endif
    partial class Assert
    {
        /// <summary>
        /// Verifies that the provided object raised <see cref="INotifyPropertyChanged.PropertyChanged"/>
        /// as a result of executing the given test code.
        /// </summary>
        /// <param name="object">The object which should raise the notification</param>
        /// <param name="propertyName">The property name for which the notification should be raised</param>
        /// <param name="testCode">The test code which should cause the notification to be raised</param>
        /// <exception cref="PropertyChangedException">Thrown when the notification is not raised</exception>
        public static void PropertyChanged(INotifyPropertyChanged @object, string propertyName, Action testCode)
        {
            Assert.GuardArgumentNotNull("object", @object);
            Assert.GuardArgumentNotNull("testCode", testCode);

            bool propertyChangeHappened = false;

            PropertyChangedEventHandler handler = (sender, args) => propertyChangeHappened |= string.IsNullOrEmpty(args.PropertyName) || propertyName.Equals(args.PropertyName, StringComparison.OrdinalIgnoreCase);

            @object.PropertyChanged += handler;

            try
            {
                testCode();
                if (!propertyChangeHappened)
                    throw new PropertyChangedException(propertyName);
            }
            finally
            {
                @object.PropertyChanged -= handler;
            }
        }

        /// <summary/>
        [EditorBrowsable(EditorBrowsableState.Never)]
        [Obsolete("You must call Assert.PropertyChangedAsync (and await the result) when testing async code.", true)]
        [SuppressMessage("Code Notifications", "RECS0083:Shows NotImplementedException throws in the quick task bar", Justification = "This is a purposeful use of NotImplementedException")]
        public static void PropertyChanged(INotifyPropertyChanged @object, string propertyName, Func<Task> testCode) { throw new NotImplementedException(); }

        /// <summary>
        /// Verifies that the provided object raised <see cref="INotifyPropertyChanged.PropertyChanged"/>
        /// as a result of executing the given test code.
        /// </summary>
        /// <param name="object">The object which should raise the notification</param>
        /// <param name="propertyName">The property name for which the notification should be raised</param>
        /// <param name="testCode">The test code which should cause the notification to be raised</param>
        /// <exception cref="PropertyChangedException">Thrown when the notification is not raised</exception>
        public static async Task PropertyChangedAsync(INotifyPropertyChanged @object, string propertyName, Func<Task> testCode)
        {
            Assert.GuardArgumentNotNull("object", @object);
            Assert.GuardArgumentNotNull("testCode", testCode);

            bool propertyChangeHappened = false;

            PropertyChangedEventHandler handler = (sender, args) => propertyChangeHappened |= string.IsNullOrEmpty(args.PropertyName) || propertyName.Equals(args.PropertyName, StringComparison.OrdinalIgnoreCase);

            @object.PropertyChanged += handler;

            try
            {
                await testCode();
                if (!propertyChangeHappened)
                    throw new PropertyChangedException(propertyName);
            }
            finally
            {
                @object.PropertyChanged -= handler;
            }
        }
    }
}