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using System;
using NUnit.Framework;
namespace Xamarin.Forms.Core.UnitTests
{
[TestFixture]
public class WeakEventManagerTests
{
static int s_count;
static void Handler(object sender, EventArgs eventArgs)
{
s_count++;
}
internal class TestEventSource
{
readonly WeakEventManager _weakEventManager;
public TestEventSource()
{
_weakEventManager = new WeakEventManager();
}
public void FireTestEvent()
{
OnTestEvent();
}
internal event EventHandler TestEvent
{
add { _weakEventManager.AddEventHandler(nameof(TestEvent), value); }
remove { _weakEventManager.RemoveEventHandler(nameof(TestEvent), value); }
}
void OnTestEvent()
{
_weakEventManager.HandleEvent(this, EventArgs.Empty, nameof(TestEvent));
}
}
internal class TestSubscriber
{
public void Subscribe(TestEventSource source)
{
source.TestEvent += SourceOnTestEvent;
}
void SourceOnTestEvent(object sender, EventArgs eventArgs)
{
Assert.Fail();
}
}
[Test]
public void AddHandlerWithEmptyEventNameThrowsException()
{
var wem = new WeakEventManager();
Assert.Throws<ArgumentNullException>(() => wem.AddEventHandler("", (sender, args) => { }));
}
[Test]
public void AddHandlerWithNullEventHandlerThrowsException()
{
var wem = new WeakEventManager();
Assert.Throws<ArgumentNullException>(() => wem.AddEventHandler("test", null));
}
[Test]
public void AddHandlerWithNullEventNameThrowsException()
{
var wem = new WeakEventManager();
Assert.Throws<ArgumentNullException>(() => wem.AddEventHandler(null, (sender, args) => { }));
}
[Test]
public void CanRemoveStaticEventHandler()
{
int beforeRun = s_count;
var source = new TestEventSource();
source.TestEvent += Handler;
source.TestEvent -= Handler;
source.FireTestEvent();
Assert.IsTrue(s_count == beforeRun);
}
[Test]
public void EventHandlerCalled()
{
var called = false;
var source = new TestEventSource();
source.TestEvent += (sender, args) => { called = true; };
source.FireTestEvent();
Assert.IsTrue(called);
}
[Test]
public void FiringEventWithoutHandlerShouldNotThrow()
{
var source = new TestEventSource();
source.FireTestEvent();
}
[Test]
public void MultipleHandlersCalled()
{
var called1 = false;
var called2 = false;
var source = new TestEventSource();
source.TestEvent += (sender, args) => { called1 = true; };
source.TestEvent += (sender, args) => { called2 = true; };
source.FireTestEvent();
Assert.IsTrue(called1 && called2);
}
[Test]
public void RemoveHandlerWithEmptyEventNameThrowsException()
{
var wem = new WeakEventManager();
Assert.Throws<ArgumentNullException>(() => wem.RemoveEventHandler("", (sender, args) => { }));
}
[Test]
public void RemoveHandlerWithNullEventHandlerThrowsException()
{
var wem = new WeakEventManager();
Assert.Throws<ArgumentNullException>(() => wem.RemoveEventHandler("test", null));
}
[Test]
public void RemoveHandlerWithNullEventNameThrowsException()
{
var wem = new WeakEventManager();
Assert.Throws<ArgumentNullException>(() => wem.RemoveEventHandler(null, (sender, args) => { }));
}
[Test]
public void RemovingNonExistentHandlersShouldNotThrow()
{
var wem = new WeakEventManager();
wem.RemoveEventHandler("fake", (sender, args) => { });
wem.RemoveEventHandler("alsofake", Handler);
}
[Test]
public void StaticHandlerShouldRun()
{
int beforeRun = s_count;
var source = new TestEventSource();
source.TestEvent += Handler;
source.FireTestEvent();
Assert.IsTrue(s_count > beforeRun);
}
[Test]
public void VerifySubscriberCanBeCollected()
{
WeakReference wr = null;
var source = new TestEventSource();
new Action(() =>
{
var ts = new TestSubscriber();
wr = new WeakReference(ts);
ts.Subscribe(source);
})();
GC.Collect();
GC.WaitForPendingFinalizers();
Assert.IsNotNull(wr);
Assert.IsFalse(wr.IsAlive);
// The handler for this calls Assert.Fail, so if the subscriber has not been collected
// the handler will be called and the test will fail
source.FireTestEvent();
}
}
}
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