8000 Add NotifyPropertyChangeBehavior by kzu · Pull Request #282 · devlooped/stunts · GitHub
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Add NotifyPropertyChangeBehavior #282

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Merged
kzu merged 4 commits into from
Oct 7, 2026
Merged

Add NotifyPropertyChangeBehavior #282

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152e578
Add NotifyPropertyChangeBehavior for INotifyPropertyChanging/INotifyP…
kzu Oct 7, 2026
b501ad9
Fix scenario test structure: implement IRunnable with Run() entry point
kzu Oct 7, 2026
930365b
Add scenario tests for AddBehavior<T> with NotifyPropertyChangeBehavior
kzu Oct 7, 2026
78b1e88
Remove redundant [assembly: Stunt] attribute: generator infers stunts…
kzu Oct 7, 2026
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228 changes: 228 additions & 0 deletions src/Stunts.UnitTests/Scenarios/NotifyPropertyChange.cs
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#pragma warning disable IDE0079
#pragma warning disable CS0436
using System;
using System.Collections.Generic;
using System.ComponentModel;
using Stunts;
using Xunit;

namespace Stunts.Scenarios.NotifyPropertyChange
{
public interface IPerson
{
string Name { get; set; }
}

/// <summary>
/// A behavior can raise INotifyPropertyChanging/INotifyPropertyChanged from
/// property setters, with per-stunt notification state.
/// </summary>
public class Test : IRunnable
{
public void Run()
{
NewValueRaisesChangingThenChanged_WithPropertyName_SetterRunsOnce();
EqualValue_RaisesNeitherEvent_ButStillRunsSetter_ByDefault();
EqualValue_SkipsSetter_WhenShortCircuitUnchanged();
ThrowingSetter_RaisesNoPropertyChanged_AndDoesNotRecordValue();
BuilderStuntsHaveIndependentNotificationState();
Unsubscribe_StopsNotifications();
GenericAddBehavior_MaterializesOnToObject();
GenericAddBehavior_OnLivePipeline_AddsInstanceImmediately();
}

public void NewValueRaisesChangingThenChanged_WithPropertyName_SetterRunsOnce()
{
var stunt = Stunt.For<IPerson, INotifyPropertyChanged, INotifyPropertyChanging>();
stunt.AddBehavior(new NotifyPropertyChangeBehavior());
var sets = new CountingBehavior();
stunt.AddBehavior(sets);
stunt.AddBehavior(new DefaultValueBehavior());
IPerson person = stunt.ToObject();

var events = new List<string>();
((INotifyPropertyChanging)person).PropertyChanging += (_, e) => events.Add("Changing:" + e.PropertyName);
((INotifyPropertyChanged)person).PropertyChanged += (_, e) => events.Add("Changed:" + e.PropertyName);

var baseline = sets.Calls;
person.Name = "Ada";

Assert.Equal(
new[] { "Changing:Name", "Changed:Name" },
events);
Assert.Equal(baseline + 1, sets.Calls);
}

public void EqualValue_RaisesNeitherEvent_ButStillRunsSetter_ByDefault()
{
var stunt = Stunt.For<IPerson, INotifyPropertyChanged, INotifyPropertyChanging>();
stunt.AddBehavior(new NotifyPropertyChangeBehavior());
var sets = new CountingBehavior();
stunt.AddBehavior(sets);
stunt.AddBehavior(new DefaultValueBehavior());
IPerson person = stunt.ToObject();

var events = new List<string>();
((INotifyPropertyChanging)person).PropertyChanging += (_, e) => events.Add("Changing:" + e.PropertyName);
((INotifyPropertyChanged)person).PropertyChanged += (_, e) => events.Add("Changed:" + e.PropertyName);

person.Name = "Ada";
var baseline = sets.Calls;
events.Clear();

person.Name = "Ada";

Assert.Empty(events);
Assert.Equal(baseline + 1, sets.Calls);
}

public void EqualValue_SkipsSetter_WhenShortCircuitUnchanged()
{
var stunt = Stunt.For<IPerson, INotifyPropertyChanged, INotifyPropertyChanging>();
stunt.AddBehavior(new NotifyPropertyChangeBehavior(shortCircuitUnchanged: true));
var sets = new CountingBehavior();
stunt.AddBehavior(sets);
stunt.AddBehavior(new DefaultValueBehavior());
IPerson person = stunt.ToObject();

var events = new List<string>();
((INotifyPropertyChanging)person).PropertyChanging += (_, e) => events.Add("Changing:" + e.PropertyName);
((INotifyPropertyChanged)person).PropertyChanged += (_, e) => events.Add("Changed:" + e.PropertyName);

person.Name = "Ada";
var baseline = sets.Calls;
events.Clear();

person.Name = "Ada";

Assert.Empty(events);
Assert.Equal(baseline, sets.Calls);
}

public void ThrowingSetter_RaisesNoPropertyChanged_AndDoesNotRecordValue()
{
var stunt = Stunt.For<IPerson, INotifyPropertyChanged, INotifyPropertyChanging>();
stunt.AddBehavior(new NotifyPropertyChangeBehavior());
var thrower = new ThrowOnceBehavior();
stunt.AddBehavior(thrower);
stunt.AddBehavior(new DefaultValueBehavior());
IPerson person = stunt.ToObject();

var events = new List<string>();
((INotifyPropertyChanging)person).PropertyChanging += (_, e) => events.Add("Changing:" + e.PropertyName);
((INotifyPropertyChanged)person).PropertyChanged += (_, e) => events.Add("Changed:" + e.PropertyName);

Assert.Throws<InvalidOperationException>(() => person.Name = "Ada");
// Changing was raised before the setter ran; Changed was not.
Assert.Equal(new[] { "Changing:Name" }, events);

// The failed write was not recorded: the next set notifies normally.
events.Clear();
person.Name = "Ada";
Assert.Equal(new[] { "Changing:Name", "Changed:Name" }, events);
}

public void BuilderStuntsHaveIndependentNotificationState()
{
var builder = Stunt.Builder();
builder.AddBehavior<NotifyPropertyChangeBehavior>();
builder.AddBehavior(new DefaultValueBehavior());

IPerson first = builder.Build<IPerson, INotifyPropertyChanged, INotifyPropertyChanging>();
IPerson second = builder.Build<IPerson, INotifyPropertyChanged, INotifyPropertyChanging>();

var firstEvents = new List<string>();
((INotifyPropertyChanged)first).PropertyChanged += (_, e) => firstEvents.Add(e.PropertyName);

second.Name = "Ada";

Assert.Empty(firstEvents);
}

public void Unsubscribe_StopsNotifications()
{
var stunt = Stunt.For<IPerson, INotifyPropertyChanged, INotifyPropertyChanging>();
stunt.AddBehavior(new NotifyPropertyChangeBehavior());
stunt.AddBehavior(new DefaultValueBehavior());
IPerson person = stunt.ToObject();

var events = new List<string>();
PropertyChangedEventHandler handler = (_, e) => events.Add(e.PropertyName);
((INotifyPropertyChanged)person).PropertyChanged += handler;

person.Name = "Ada";
Assert.Equal(new[] { "Name" }, events);

((INotifyPropertyChanged)person).PropertyChanged -= handler;
person.Name = "Grace";

Assert.Equal(new[] { "Name" }, events);
}

public void GenericAddBehavior_MaterializesOnToObject()
{
var stunt = Stunt.For<IPerson, INotifyPropertyChanged, INotifyPropertyChanging>();
stunt.AddBehavior<NotifyPropertyChangeBehavior>();
stunt.AddBehavior(new DefaultValueBehavior());
IPerson person = stunt.ToObject();

Assert.IsType<NotifyPropertyChangeBehavior>(stunt.Behaviors[0]);

var events = new List<string>();
((INotifyPropertyChanged)person).PropertyChanged += (_, e) => events.Add(e.PropertyName);

person.Name = "Ada";

Assert.Equal(new[] { "Name" }, events);
}

public void GenericAddBehavior_OnLivePipeline_AddsInstanceImmediately()
{
var stunt = Stunt.For<IPerson, INotifyPropertyChanged, INotifyPropertyChanging>();
IPerson person = stunt.ToObject();

stunt.AddBehavior<NotifyPropertyChangeBehavior>();
stunt.AddBehavior(new DefaultValueBehavior());

Assert.IsType<NotifyPropertyChangeBehavior>(stunt.Behaviors[0]);

var events = new List<string>();
((INotifyPropertyChanged)person).PropertyChanged += (_, e) => events.Add(e.PropertyName);

person.Name = "Ada";

Assert.Equal(new[] { "Name" }, events);
}

class CountingBehavior : IStuntBehavior
{
public int Calls;

public bool AppliesTo(IMethodInvocation invocation) => true;

public IMethodReturn Execute(IMethodInvocation invocation, ExecuteHandler next)
{
Calls++;
return next(invocation, next);
}
}

class ThrowOnceBehavior : IStuntBehavior
{
bool thrown;

public bool AppliesTo(IMethodInvocation invocation)
=> invocation.MethodBase.Name.StartsWith("set_", StringComparison.Ordinal);

public IMethodReturn Execute(IMethodInvocation invocation, ExecuteHandler next)
{
if (!thrown)
{
thrown = true;
throw new InvalidOperationException("Simulated setter failure.");
}
return next(invocation, next);
}
}
}
}
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