From 1823c1ad1463aa30deb289bc9538a68a5316164b Mon Sep 17 00:00:00 2001
From: "E.Z. Hart" <hartez@users.noreply.github.com>
Date: Wed, 10 Aug 2016 05:51:33 -0600
Subject: Unit tests for the PCL WeakEventManager (#280)

---
 .../WeakEventManagerTests.cs                       | 189 +++++++++++++++++++++
 .../Xamarin.Forms.Core.UnitTests.csproj            |   1 +
 2 files changed, 190 insertions(+)
 create mode 100644 Xamarin.Forms.Core.UnitTests/WeakEventManagerTests.cs

(limited to 'Xamarin.Forms.Core.UnitTests')

diff --git a/Xamarin.Forms.Core.UnitTests/WeakEventManagerTests.cs b/Xamarin.Forms.Core.UnitTests/WeakEventManagerTests.cs
new file mode 100644
index 00000000..8300613a
--- /dev/null
+++ b/Xamarin.Forms.Core.UnitTests/WeakEventManagerTests.cs
@@ -0,0 +1,189 @@
+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();
+		}
+	}
+}
\ No newline at end of file
diff --git a/Xamarin.Forms.Core.UnitTests/Xamarin.Forms.Core.UnitTests.csproj b/Xamarin.Forms.Core.UnitTests/Xamarin.Forms.Core.UnitTests.csproj
index 27fc07ee..4eae5d53 100644
--- a/Xamarin.Forms.Core.UnitTests/Xamarin.Forms.Core.UnitTests.csproj
+++ b/Xamarin.Forms.Core.UnitTests/Xamarin.Forms.Core.UnitTests.csproj
@@ -152,6 +152,7 @@
     <Compile Include="TypeUnitTests.cs" />
     <Compile Include="ViewCellTests.cs" />
     <Compile Include="ViewUnitTests.cs" />
+    <Compile Include="WeakEventManagerTests.cs" />
     <Compile Include="WebViewUnitTests.cs" />
     <Compile Include="ImageSourceTests.cs" />
     <Compile Include="DataTemplateTests.cs" />
-- 
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