StyleTests.cs

using NUnit.Framework;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Xamarin.Forms.Internals;

namespace Xamarin.Forms.Core.UnitTests
{
	[TestFixture]
	public class StyleTests : BaseTestFixture
	{
		internal class Logger : LogListener
		{
			public IReadOnlyList<string> Messages {
				get { return messages; }
			}

			public override void Warning(string category, string message)
			{
				messages.Add("[" + category + "] " + message);
			}

			readonly List<string> messages = new List<string>();
		}

		internal Logger log;

		[SetUp]
		public override void Setup ()
		{
			base.Setup ();
			log = new Logger();
			Device.PlatformServices = new MockPlatformServices ();
			Log.Listeners.Add(log);
		}

		[TearDown]
		public override void TearDown()
		{
			base.TearDown();
			Log.Listeners.Remove(log);
			Application.Current = null;
		}

		[Test]
		public void ApplyUnapplyStyle ()
		{
			var style = new Style (typeof(VisualElement)) {
				Setters = {
					new Setter { Property = Label.TextProperty, Value = "foo" },
					new Setter { Property = VisualElement.BackgroundColorProperty, Value = Color.Pink },
				}
			};

			var label = new Label {
				Style = style
			};
			Assert.AreEqual ("foo", label.Text);
			Assert.AreEqual (Color.Pink, label.BackgroundColor);

			label.Style = null;
			Assert.AreEqual (Label.TextProperty.DefaultValue, label.Text);
			Assert.AreEqual (VisualElement.BackgroundColorProperty.DefaultValue, label.BackgroundColor);
		}

		[Test]
		public void BindingAndDynamicResourcesInStyle ()
		{
			var style = new Style (typeof(VisualElement)) {
				Setters = {
					new Setter { Property = VisualElement.IsEnabledProperty, Value = false }
				}
			};
			style.Setters.AddBinding (Label.TextProperty, new Binding ("foo"));
			style.Setters.AddDynamicResource (VisualElement.BackgroundColorProperty, "qux");

			var label = new Label {
				Style = style
			};

			label.BindingContext = new {foo = "FOO"};
			Assert.AreEqual ("FOO", label.Text);

			label.Resources = new ResourceDictionary {
				{"qux", Color.Pink}
			};
			Assert.AreEqual (Color.Pink, label.BackgroundColor);

			label.Style = null;
			Assert.AreEqual (Label.TextProperty.DefaultValue, label.Text);
			Assert.AreEqual (VisualElement.BackgroundColorProperty.DefaultValue, label.BackgroundColor);
		}

		[Test]
		public void StyleCanBeAppliedMultipleTimes ()
		{
			var style = new Style (typeof(VisualElement)) {
				Setters = {
					new Setter{ Property = VisualElement.IsEnabledProperty, Value = false }
				}
			};
			style.Setters.AddBinding (Label.TextProperty, new Binding ("foo"));
			style.Setters.AddDynamicResource (VisualElement.BackgroundColorProperty, "qux");

			var label0 = new Label {
				Style = style
			};
			var label1 = new Label {
				Style = style
			};

			label0.BindingContext = label1.BindingContext = new {foo = "FOO"};
			label0.Resources = label1.Resources = new ResourceDictionary {
				{"qux", Color.Pink}
			};

			Assert.AreEqual ("FOO", label0.Text);
			Assert.AreEqual ("FOO", label1.Text);

			Assert.AreEqual (Color.Pink, label0.BackgroundColor);
			Assert.AreEqual (Color.Pink, label1.BackgroundColor);

			label0.Style = label1.Style = null;

			Assert.AreEqual (Label.TextProperty.DefaultValue, label0.Text);
			Assert.AreEqual (Label.TextProperty.DefaultValue, label1.Text);
			Assert.AreEqual (VisualElement.BackgroundColorProperty.DefaultValue, label0.BackgroundColor);
			Assert.AreEqual (VisualElement.BackgroundColorProperty.DefaultValue, label1.BackgroundColor);
		}

		[Test]
		public void BaseStyleIsAppliedUnapplied ()
		{
			var baseStyle = new Style (typeof(VisualElement)) {
				Setters = {
					new Setter { Property = Label.TextProperty, Value = "baseStyle" },
				}
			};
			var style = new Style(typeof(Label)) {
				BasedOn = baseStyle,
			};

			var label = new Label {
				Style = style
			};
			Assert.AreEqual ("baseStyle", label.Text);

			label.Style = null;
			Assert.AreEqual (Label.TextProperty.DefaultValue, label.Text);
		}

		[Test]
		public void StyleOverrideBaseStyle ()
		{
			var baseStyle = new Style(typeof(VisualElement)) {
				Setters = {
					new Setter{Property= Label.TextProperty,Value= "baseStyle" },
				}
			};
			var style = new Style(typeof(VisualElement)) {
				BasedOn = baseStyle,
				Setters = {
					new Setter{Property= Label.TextProperty,Value= "style" },
				}
			};

			var label = new Label {
				Style = style
			};
			Assert.AreEqual ("style", label.Text);

			label.Style = null;
			Assert.AreEqual (Label.TextProperty.DefaultValue, label.Text);
		}

		[Test]
		public void AddImplicitStyleToResourceDictionary ()
		{
			var rd = new ResourceDictionary { 
				new Style (typeof(Label)) { Setters = {
						new Setter { Property = Label.TextColorProperty, Value = Color.Pink },
					}
				},
				{ "foo", "FOO" }, 
				{"labelStyle", new Style (typeof(Label)) { Setters = {
							new Setter { Property = Label.TextColorProperty, Value = Color.Purple }
						}
					}
				}
			};

			Assert.AreEqual (3, rd.Count);
			Assert.Contains ("Xamarin.Forms.Label", (System.Collections.ICollection)rd.Keys);
		}

		[Test]
		public void ImplicitStylesAreAppliedOnSettingRD ()
		{
			var rd = new ResourceDictionary { 
				new Style (typeof(Label)) { Setters = {
						new Setter { Property = Label.TextColorProperty, Value = Color.Pink },
					}
				},
				{ "foo", "FOO" }, 
				{"labelStyle", new Style (typeof(Label)) { Setters = {
							new Setter { Property = Label.TextColorProperty, Value = Color.Purple }
						}
					}
				}
			};

			var label = new Label ();
			var layout = new StackLayout { Children = { label } };

			Assert.AreEqual (label.TextColor, Label.TextColorProperty.DefaultValue);
			layout.Resources = rd;
			Assert.AreEqual (label.TextColor, Color.Pink);
		}

		[Test]
		public void ImplicitStylesAreAppliedOnSettingParrent ()
		{
			var rd = new ResourceDictionary { 
				new Style (typeof(Label)) { Setters = {
						new Setter { Property = Label.TextColorProperty, Value = Color.Pink },
					}
				},
				{ "foo", "FOO" }, 
				{"labelStyle", new Style (typeof(Label)) { Setters = {
							new Setter { Property = Label.TextColorProperty, Value = Color.Purple }
						}
					}
				}
			};

			var label = new Label ();
			var layout = new StackLayout ();
			layout.Resources = rd;

			Assert.AreEqual (label.TextColor, Label.TextColorProperty.DefaultValue);
			layout.Children.Add (label);
			Assert.AreEqual (label.TextColor, Color.Pink);
		}

		[Test]
		public void ImplicitStylesOverridenByStyle ()
		{
			var rd = new ResourceDictionary { 
				new Style (typeof(Label)) { Setters = {
						new Setter { Property = Label.TextColorProperty, Value = Color.Pink },
					}
				},
				{ "foo", "FOO" }, 
				{"labelStyle", new Style (typeof(Label)) { Setters = {
							new Setter { Property = Label.TextColorProperty, Value = Color.Purple }
						}
					}
				}
			};

			var label = new Label ();
			label.SetDynamicResource (VisualElement.StyleProperty, "labelStyle");
			var layout = new StackLayout { Children = { label }, Resources = rd };

			Assert.AreEqual (label.TextColor, Color.Purple);
		}

		[Test]
		public void UnsettingStyleReApplyImplicit ()
		{
			var rd = new ResourceDictionary { 
				new Style (typeof(Label)) { Setters = {
						new Setter { Property = Label.TextColorProperty, Value = Color.Pink },
					}
				},
				{ "foo", "FOO" }, 
				{"labelStyle", new Style (typeof(Label)) { Setters = {
							new Setter { Property = Label.TextColorProperty, Value = Color.Purple }
						}
					}
				}
			};

			var label = new Label ();
			label.SetDynamicResource (VisualElement.StyleProperty, "labelStyle");
			var layout = new StackLayout { Children = { label }, Resources = rd };

			Assert.AreEqual (label.TextColor, Color.Purple);
			label.Style = null;
			Assert.AreEqual (label.TextColor, Color.Pink);
		}

		[Test]
		public void DynamicStyle ()
		{
			var baseStyle0 = new Style(typeof(Label)) {
				Setters = {
					new Setter {Property = Label.TextProperty, Value = "foo"},
					new Setter {Property = Label.TextColorProperty, Value = Color.Pink}
				}
			};
			var baseStyle1 = new Style(typeof(Label)) {
				Setters = {
					new Setter {Property = Label.TextProperty, Value = "bar"},
					new Setter {Property = Label.TextColorProperty, Value = Color.Purple}
				}
			};
			var style = new Style (typeof(Label)) {
				BaseResourceKey = "basestyle",
				Setters = {
					new Setter { Property = Label.BackgroundColorProperty, Value = Color.Red },
					new Setter { Property = Label.TextColorProperty, Value = Color.Red },
				}
			};

			var label0 = new Label {
				Style = style
			};

			Assert.AreEqual (Color.Red, label0.BackgroundColor);
			Assert.AreEqual (Color.Red, label0.TextColor);
			Assert.AreEqual (Label.TextProperty.DefaultValue, label0.Text);

			var layout0 = new StackLayout {
				Resources = new ResourceDictionary {
					{"basestyle", baseStyle0}
				},
				Children = {
					label0
				}
			};

			Assert.AreEqual (Color.Red, label0.BackgroundColor);
			Assert.AreEqual (Color.Red, label0.TextColor);
			Assert.AreEqual ("foo", label0.Text);

			var label1 = new Label {
				Style = style
			};

			Assert.AreEqual (Color.Red, label1.BackgroundColor);
			Assert.AreEqual (Color.Red, label1.TextColor);
			Assert.AreEqual (Label.TextProperty.DefaultValue, label1.Text);

			var layout1 = new StackLayout {
				Children = {
					label1
				}
			};
			layout1.Resources = new ResourceDictionary {
				{"basestyle", baseStyle1}
			};

			Assert.AreEqual (Color.Red, label1.BackgroundColor);
			Assert.AreEqual (Color.Red, label1.TextColor);
			Assert.AreEqual ("bar", label1.Text);
		}

		[Test]
		public void TestTriggersAndBehaviors ()
		{
			var behavior = new MockBehavior<Entry> ();
			var style = new Style (typeof(Entry)) { 
				Setters = {
					new Setter {Property = Entry.TextProperty, Value = "foo"},
				},
				Triggers = {
					new Trigger (typeof (VisualElement)) {Property = Entry.IsPasswordProperty, Value=true, Setters = {
							new Setter {Property = VisualElement.ScaleProperty, Value = 2d},
						}}
				},
				Behaviors = {
					behavior,
				}
			};

			var entry = new Entry { Style = style };
			Assert.AreEqual ("foo", entry.Text);
			Assert.AreEqual (1d, entry.Scale);

			entry.IsPassword = true;
			Assert.AreEqual (2d, entry.Scale);

			Assert.True (behavior.attached);

			entry.Style = null;

			Assert.AreEqual (Entry.TextProperty.DefaultValue, entry.Text);
			Assert.True (entry.IsPassword);
			Assert.AreEqual (1d, entry.Scale);
			Assert.True (behavior.detached);
		}

		[Test]
		//Issue #2124
		public void SetValueOverridesStyle ()
		{
			var style = new Style (typeof(Label)) {
				Setters = {
					new Setter {Property = Label.TextColorProperty, Value=Color.Black},
				}
			};

			var label = new Label { TextColor = Color.White, Style = style };
			Assert.AreEqual (Color.White, label.TextColor);
		}

		[Test]
		//https://bugzilla.xamarin.com/show_bug.cgi?id=28556
		public void TriggersAppliedAfterSetters ()
		{
			var style = new Style (typeof(Entry)) {
				Setters = {
					new Setter { Property = Entry.TextColorProperty, Value = Color.Yellow }
				},
				Triggers = {
					new Trigger (typeof(Entry)) {
						Property = VisualElement.IsEnabledProperty,
						Value = false,
						Setters = {
							new Setter { Property = Entry.TextColorProperty, Value = Color.Red }
						},
					}
				},
			};

			var entry = new Entry { IsEnabled = false, Style = style };
			Assert.AreEqual (Color.Red, entry.TextColor);
			entry.IsEnabled = true;
			Assert.AreEqual (Color.Yellow, entry.TextColor);
		}

		[Test]
		//https://bugzilla.xamarin.com/show_bug.cgi?id=31207
		public async void StyleDontHoldStrongReferences ()
		{
			var style = new Style (typeof(Label));
			var label = new Label ();
			var tracker = new WeakReference (label);
			label.Style = style;
			label = null;

			await Task.Delay (10);
			GC.Collect ();

			Assert.False (tracker.IsAlive);
			Assert.NotNull (style);
		}

		class MyLabel : Label
		{ 
		}

		class MyButton : Button
		{
		}

		[Test]
		public void ImplicitStylesNotAppliedToDerivedTypesByDefault ()
		{
			var style = new Style (typeof (Label)) {
				Setters = {
					new Setter { Property = Label.TextProperty, Value = "Foo" }
				}
			};
			var view = new ContentView {
				Resources = new ResourceDictionary { style },
				Content = new MyLabel (),
			};

			Assert.AreEqual (Label.TextProperty.DefaultValue, ((MyLabel)view.Content).Text);
		}

		[Test]
		public void ImplicitStylesAreAppliedToDerivedIfSpecified ()
		{
			var style = new Style (typeof (Label)) {
				Setters = {
					new Setter { Property = Label.TextProperty, Value = "Foo" }
				},
				ApplyToDerivedTypes = true
			};
			var view = new ContentView {
				Resources = new ResourceDictionary { style },
				Content = new MyLabel (),
			};

			Assert.AreEqual ("Foo", ((MyLabel)view.Content).Text);
		}

		[Test]
		public void ClassStylesAreApplied ()
		{ 
			var classstyle = new Style (typeof (Label)) {
				Setters = {
					new Setter { Property = Label.TextProperty, Value = "Foo" }
				},
				Class = "fooClass",
			};
			var style = new Style (typeof (Label)) {
				Setters = {
					new Setter { Property = Label.TextColorProperty, Value = Color.Red }
				},
			};
			var view = new ContentView {
				Resources = new ResourceDictionary { classstyle },
				Content = new Label { 
					StyleClass = new [] {"fooClass"},
					Style = style
				}
			};
			Assert.AreEqual ("Foo", ((Label)view.Content).Text);
			Assert.AreEqual (Color.Red, ((Label)view.Content).TextColor);
		}

		[Test]
		public void ImplicitStylesNotAppliedByDefaultIfAStyleExists ()
		{ 
			var implicitstyle = new Style (typeof (Label)) {
				Setters = {
					new Setter { Property = Label.TextProperty, Value = "Foo" }
				},
			};
			var style = new Style (typeof (Label)) {
				Setters = {
					new Setter { Property = Label.TextColorProperty, Value = Color.Red }
				},
			};
			var view = new ContentView {
				Resources = new ResourceDictionary { implicitstyle },
				Content = new Label { 
					Style = style
				}
			};
			Assert.AreEqual (Label.TextProperty.DefaultValue, ((Label)view.Content).Text);
			Assert.AreEqual (Color.Red, ((Label)view.Content).TextColor);
		}

		[Test]
		public void ImplicitStylesAppliedIfStyleCanCascade ()
		{ 
			var implicitstyle = new Style (typeof (Label)) {
				Setters = {
					new Setter { Property = Label.TextProperty, Value = "Foo" }
				},
			};
			var style = new Style (typeof (Label)) {
				Setters = {
					new Setter { Property = Label.TextColorProperty, Value = Color.Red },
				},
				CanCascade = true
			};
			var view = new ContentView {
				Resources = new ResourceDictionary { implicitstyle },
				Content = new Label { 
					Style = style
				}
			};
			Assert.AreEqual ("Foo", ((Label)view.Content).Text);
			Assert.AreEqual (Color.Red, ((Label)view.Content).TextColor);
		}

		[Test]
		public void MultipleStylesCanShareTheSameClassName ()
		{
			var buttonStyle = new Style (typeof(Button)) {
				Setters = {
					new Setter { Property = Button.TextColorProperty, Value = Color.Pink },
				},
				Class = "pink",
				ApplyToDerivedTypes = true,
			};
			var labelStyle = new Style (typeof(Label)) {
				Setters = {
					new Setter { Property = Button.BackgroundColorProperty, Value = Color.Pink },
				},
				Class = "pink",
				ApplyToDerivedTypes = false,
			};


			var button = new Button {
				StyleClass = new [] {"pink"},
			};
			var myButton = new MyButton {
				StyleClass = new [] {"pink"},
			};

			var label = new Label {
				StyleClass = new [] {"pink"},
			};
			var myLabel = new MyLabel {
				StyleClass = new [] {"pink"},
			};


			new StackLayout {
				Resources = new ResourceDictionary {buttonStyle, labelStyle},
				Children = {
					button,
					label,
					myLabel,
					myButton,
				}
			};

			Assert.AreEqual (Color.Pink, button.TextColor);
			Assert.AreEqual (Color.Default, button.BackgroundColor);

			Assert.AreEqual (Color.Pink, myButton.TextColor);
			Assert.AreEqual (Color.Default, myButton.BackgroundColor);

			Assert.AreEqual (Color.Pink, label.BackgroundColor);
			Assert.AreEqual (Color.Default, label.TextColor);

			Assert.AreEqual (Color.Default, myLabel.BackgroundColor);
			Assert.AreEqual (Color.Default, myLabel.TextColor);
		}

		[Test]
		public void StyleClassAreCorrecltyMerged ()
		{
			var buttonStyle = new Style (typeof(Button)) {
				Setters = {
					new Setter { Property = Button.TextColorProperty, Value = Color.Pink },
				},
				Class = "pink",
				ApplyToDerivedTypes = true,
			};
			var labelStyle = new Style (typeof(Label)) {
				Setters = {
					new Setter { Property = Button.BackgroundColorProperty, Value = Color.Pink },
				},
				Class = "pink",
				ApplyToDerivedTypes = false,
			};

			var button = new Button {
				StyleClass = new [] {"pink"},
			};
			var label = new Label {
				StyleClass = new [] {"pink"},
			};

			var cv = new ContentView {
				Resources = new ResourceDictionary {buttonStyle},
				Content = new StackLayout {
					Resources = new ResourceDictionary {labelStyle},
					Children = {
						button,
						label,
					}
				}
			};

			Assert.AreEqual (Color.Pink, button.TextColor);
			Assert.AreEqual (Color.Default, button.BackgroundColor);

			Assert.AreEqual (Color.Pink, label.BackgroundColor);
			Assert.AreEqual (Color.Default, label.TextColor);
		}

		[Test]
		public void StyleClassAreCorrecltyMergedForAlreadyParentedPArents ()
		{
			var buttonStyle = new Style (typeof (Button)) {
				Setters = {
						new Setter { Property = Button.TextColorProperty, Value = Color.Pink },
					},
				Class = "pink",
				ApplyToDerivedTypes = true,
			};
			var labelStyle = new Style (typeof (Label)) {
				Setters = {
						new Setter { Property = Button.BackgroundColorProperty, Value = Color.Pink },
					},
				Class = "pink",
				ApplyToDerivedTypes = false,
			};

			var button = new Button {
				StyleClass = new [] {"pink"},
			};
			var label = new Label {
				StyleClass = new [] {"pink"},
			};

			var cv = new ContentView {
				Resources = new ResourceDictionary { buttonStyle },
				Content = new StackLayout {
					Resources = new ResourceDictionary { labelStyle },
				}
			};

			(cv.Content as StackLayout).Children.Add (button);
			(cv.Content as StackLayout).Children.Add (label);

			Assert.AreEqual (Color.Pink, button.TextColor);
			Assert.AreEqual (Color.Default, button.BackgroundColor);

			Assert.AreEqual (Color.Pink, label.BackgroundColor);
			Assert.AreEqual (Color.Default, label.TextColor);
		}

		[Test]
		public void MultipleStyleClassAreApplied ()
		{
			var pinkStyle = new Style (typeof (Button)) {
				Setters = {
					new Setter { Property = Button.TextColorProperty, Value = Color.Pink },
				},
				Class = "pink",
				ApplyToDerivedTypes = true,
			};
			var bigStyle = new Style (typeof (Button)) {
				Setters = {
					new Setter { Property = Button.FontSizeProperty, Value = 20 },
				},
				Class = "big",
				ApplyToDerivedTypes = true,
			};
			var button = new Button {
				StyleClass = new [] {"pink", "big"},
			};

			new ContentView {
				Resources = new ResourceDictionary { pinkStyle, bigStyle },
				Content = button
			};

			Assert.AreEqual (Color.Pink, button.TextColor);
			Assert.AreEqual (20d, button.FontSize);
		}

		[Test]
		public void ReplacingResourcesDoesNotOverrideManuallySetProperties()
		{
			var label0 = new Label {
				TextColor = Color.Pink
			};
			var label1 = new Label();

			Assume.That(label0.TextColor, Is.EqualTo(Color.Pink));
			Assume.That(label1.TextColor, Is.EqualTo(Color.Default));

			var rd0 = new ResourceDictionary {
				new Style (typeof(Label)) {
					Setters = {
						new Setter {Property = Label.TextColorProperty, Value = Color.Olive}
					}
				}
			};
			var rd1 = new ResourceDictionary {
				new Style (typeof(Label)) {
					Setters = {
						new Setter {Property = Label.TextColorProperty, Value = Color.Lavender}
					}
				}
			};

			var mockApp = new MockApplication();
			Application.Current = mockApp;
			mockApp.Resources = rd0;

			var layout = new StackLayout { 
				Children = {
					label0,
					label1,
				}
			};

			mockApp.MainPage = new ContentPage { Content = layout};
			//Assert.That(label0.TextColor, Is.EqualTo(Color.Pink));
			//Assert.That(label1.TextColor, Is.EqualTo(Color.Default));

			Assert.That(label0.TextColor, Is.EqualTo(Color.Pink));
			Assert.That(label1.TextColor, Is.EqualTo(Color.Olive));

			mockApp.Resources = rd1;
			Assert.That(label0.TextColor, Is.EqualTo(Color.Pink));
			Assert.That(label1.TextColor, Is.EqualTo(Color.Lavender));
		}
		
		[Test]
		public void ImplicitInheritedStyleForTemplatedElementIsAppliedCorrectlyForContentPage()
		{
			var controlTemplate = new ControlTemplate(typeof(ContentPresenter));

			var rd0 = new ResourceDictionary {
				new Style (typeof(ContentPage)) {
					Setters = {
						new Setter {Property = TemplatedPage.ControlTemplateProperty, Value = controlTemplate}
					},
					ApplyToDerivedTypes = true
				}
			};

			var mockApp = new MockApplication();
			mockApp.Resources = rd0;
			mockApp.MainPage = new MyPage()
			{
				Content = new Button()
			};

			Application.Current = mockApp;

			var parentPage = (ContentPage)mockApp.MainPage;
			var pageContent = parentPage.Content;
			Assert.That(Equals(pageContent?.Parent, parentPage));
		}

		[Test]
		public void ImplicitInheritedStyleForTemplatedElementIsAppliedCorrectlyForContentView()
		{
			var controlTemplate = new ControlTemplate(typeof(ContentPresenter));

			var rd0 = new ResourceDictionary {
				new Style (typeof(ContentView)) {
					Setters = {
						new Setter {Property = TemplatedView.ControlTemplateProperty, Value = controlTemplate}
					},
					ApplyToDerivedTypes = true
				}
			};

			var mockApp = new MockApplication();
			mockApp.Resources = rd0;
			mockApp.MainPage = new ContentPage()
			{
				Content = new MyContentView()
				{
					Content = new Button()
				}
			};

			Application.Current = mockApp;

			var parentView = (ContentView)((ContentPage)mockApp.MainPage).Content;
			var content = parentView.Content;
			Assert.That(Equals(content?.Parent, parentView));
		}
	
		class MyPage : ContentPage
		{
		}

		class MyContentView : ContentView
		{
		}

		[Test]
		public void MismatchTargetTypeLogsWarningMessage1()
		{
			var s = new Style(typeof(Button));
			var t = new View();

			t.Style = s;
			
			Assert.AreEqual(log.Messages.Count, 1);
			Assert.AreEqual(log.Messages.FirstOrDefault(), $"[Styles] Style TargetType Xamarin.Forms.Button is not compatible with element target type Xamarin.Forms.View");
		}

		[Test]
		public void MismatchTargetTypeLogsWarningMessage2()
		{
			var s = new Style(typeof(Button));
			var t = new Label();

			t.Style = s;

			Assert.AreEqual(log.Messages.Count, 1);
			Assert.AreEqual(log.Messages.FirstOrDefault(), $"[Styles] Style TargetType Xamarin.Forms.Button is not compatible with element target type Xamarin.Forms.Label");
		}

		[Test]
		public void MatchTargetTypeDoesntLogWarningMessage()
		{
			var s = new Style(typeof(View));
			var t = new Button();

			t.Style = s;

			Assert.That(log.Messages.Count, Is.EqualTo(0),
				"A warning was logged: " + log.Messages.FirstOrDefault());
    	}
	}
}