/// <summary>
/// Asserts that the execution of the provided action raises the property changed event.
/// </summary>
/// <typeparam name="T">The type of the observable.</typeparam>
/// <param name="observable">The observable which should raise the property changed event.</param>
/// <param name="expression">A simple expression which identifies the property (e.g. x => x.Name).</param>
/// <param name="raisePropertyChanged">An action that results in a property changed event of the observable.</param>
/// <param name="expectedChangedCount">The expected count of PropertyChanged events.</param>
/// <param name="expectedChangedCountMode">The mode defines how the expected changed count is used as assert condition.</param>
/// <exception cref="AssertException">This exception is thrown when no or more than one property changed event was
/// raised by the observable or the sender object of the event was not the observable object.</exception>
public static void PropertyChangedEvent <T>(T observable, Expression <Func <T, object> > expression, Action raisePropertyChanged, int expectedChangedCount,
ExpectedChangedCountMode expectedChangedCountMode)
where T : class, INotifyPropertyChanged
{
if (observable == null)
{
throw new ArgumentNullException(nameof(observable));
}
if (expression == null)
{
throw new ArgumentNullException(nameof(expression));
}
if (raisePropertyChanged == null)
{
throw new ArgumentNullException(nameof(raisePropertyChanged));
}
if (expectedChangedCount < 0)
{
throw new ArgumentOutOfRangeException(nameof(expectedChangedCount), "A negative number is not allowed.");
}
string propertyName = GetProperty(expression).Name;
int propertyChangedCount = 0;
PropertyChangedEventHandler propertyChangedHandler = (sender, e) =>
{
if (observable != sender)
{
throw new AssertException("The sender object of the event isn't the observable");
}
if (e.PropertyName == propertyName)
{
propertyChangedCount++;
}
};
observable.PropertyChanged += propertyChangedHandler;
raisePropertyChanged();
observable.PropertyChanged -= propertyChangedHandler;
if (propertyChangedCount < expectedChangedCount && expectedChangedCountMode != ExpectedChangedCountMode.AtMost)
{
throw new AssertException(string.Format(null,
"The PropertyChanged event for the property '{0}' was raised {1} times. Expected is {2} times{3}.",
propertyName, propertyChangedCount, expectedChangedCount,
expectedChangedCountMode == ExpectedChangedCountMode.AtLeast ? " or more" : ""));
}
else if (propertyChangedCount > expectedChangedCount && expectedChangedCountMode != ExpectedChangedCountMode.AtLeast)
{
throw new AssertException(string.Format(null,
"The PropertyChanged event for the property '{0}' was raised {1} times. Expected is {2} times{3}.",
propertyName, propertyChangedCount, expectedChangedCount,
expectedChangedCountMode == ExpectedChangedCountMode.AtMost ? " or less" : ""));
}
}
/// <summary>
/// Asserts that the execution of the provided action raises the CanExecuteChanged event of the command.
/// </summary>
/// <param name="command">The command.</param>
/// <param name="raiseCanExecuteChanged">An action that results in a CanExecuteChanged event of the command.</param>
/// <param name="expectedChangedCount">The expected count of CanExecuteChanged events.</param>
/// <param name="expectedChangedCountMode">The mode defines how the expected changed count is used as assert condition.</param>
/// <exception cref="AssertException">This exception is thrown when no or more than one CanExecuteChanged event was
/// raised by the command or the sender object of the event was not the command object.</exception>
public static void CanExecuteChangedEvent(ICommand command, Action raiseCanExecuteChanged, int expectedChangedCount,
ExpectedChangedCountMode expectedChangedCountMode)
{
if (command == null)
{
throw new ArgumentNullException(nameof(command));
}
if (raiseCanExecuteChanged == null)
{
throw new ArgumentNullException(nameof(raiseCanExecuteChanged));
}
if (expectedChangedCount < 0)
{
throw new ArgumentOutOfRangeException(nameof(expectedChangedCount), "A negative number is not allowed.");
}
int canExecuteChangedCount = 0;
EventHandler canExecuteChangedHandler = (sender, e) =>
{
if (command != sender)
{
throw new AssertException("The sender object of the event isn't the command");
}
canExecuteChangedCount++;
};
command.CanExecuteChanged += canExecuteChangedHandler;
raiseCanExecuteChanged();
command.CanExecuteChanged -= canExecuteChangedHandler;
if (canExecuteChangedCount < expectedChangedCount && expectedChangedCountMode != ExpectedChangedCountMode.AtMost)
{
throw new AssertException(string.Format(null, "The CanExecuteChanged event was raised {0} times. Expected is {1} times{2}.",
canExecuteChangedCount, expectedChangedCount,
expectedChangedCountMode == ExpectedChangedCountMode.AtLeast ? " or more" : ""));
}
else if (canExecuteChangedCount > expectedChangedCount && expectedChangedCountMode != ExpectedChangedCountMode.AtLeast)
{
throw new AssertException(string.Format(null, "The CanExecuteChanged event was raised {0} times. Expected is {1} times{2}.",
canExecuteChangedCount, expectedChangedCount,
expectedChangedCountMode == ExpectedChangedCountMode.AtMost ? " or less" : ""));
}
}
