Fix xUnit warnings

tests/Avalonia.Base.UnitTests/Layout/LayoutableTests_LayoutRounding.cs

@@ -112,7 +112,7 @@ namespace Avalonia.Base.UnitTests.Layout
         {
             if (!expected.NearlyEquals(actual))
             {
-                throw EqualException.ForMismatchedValues(expected, actual);
+                throw EqualException.ForMismatchedValues(expected.ToString(), actual.ToString());
             }
         }
 
@@ -120,7 +120,7 @@ namespace Avalonia.Base.UnitTests.Layout
         {
             if (!expected.NearlyEquals(actual))
             {
-                throw EqualException.ForMismatchedValues(expected, actual);
+                throw EqualException.ForMismatchedValues(expected.ToString(), actual.ToString());
             }
         }
 

tests/Avalonia.IntegrationTests.Appium/WindowTests.cs

@@ -459,17 +459,13 @@ namespace Avalonia.IntegrationTests.Appium
                 // WindowStartupLocation needs to be calculated before the window is shown, meaning that
                 // the position of a centered window can be off by a bit. From initial testing, looks
                 // like this shouldn't be more than 10 pixels.
-                if (Math.Abs(expected.X - actual.X) > 10)
-                    throw EqualException.ForMismatchedValues(expected, actual);
-                if (Math.Abs(expected.Y - actual.Y) > 10)
-                    throw EqualException.ForMismatchedValues(expected, actual);
+                Assert.Equal(expected.X, actual.X, 10.0);
+                Assert.Equal(expected.Y, actual.Y, 10.0);
             }
             else if (RuntimeInformation.IsOSPlatform(OSPlatform.OSX))
             {
-                if (Math.Abs(expected.X - actual.X) > 15)
-                    throw EqualException.ForMismatchedValues(expected, actual);
-                if (Math.Abs(expected.Y - actual.Y) > 15)
-                    throw EqualException.ForMismatchedValues(expected, actual);
+                Assert.Equal(expected.X, actual.X, 15.0);
+                Assert.Equal(expected.Y, actual.Y, 15.0);
             }
             else
             {