diff --git a/src/Mahapps.Metro.Tests/Tests/NumericUpDownTests.cs b/src/Mahapps.Metro.Tests/Tests/NumericUpDownTests.cs
index f2a625150e..fb6a977613 100644
--- a/src/Mahapps.Metro.Tests/Tests/NumericUpDownTests.cs
+++ b/src/Mahapps.Metro.Tests/Tests/NumericUpDownTests.cs
@@ -11,8 +11,35 @@
 
 namespace MahApps.Metro.Tests
 {
-    public class NumericUpDownTests : AutomationTestBase
+    public class NumericUpDownTests : AutomationTestBase, IAsyncLifetime
     {
+        private NumericUpDownWindow window;
+        private TextBox textBox;
+        private RepeatButton numUp;
+        private RepeatButton numDown;
+
+        /// <summary>
+        /// Called immediately after the class has been created, before it is used.
+        /// </summary>
+        public async Task InitializeAsync()
+        {
+            await TestHost.SwitchToAppThread();
+            this.window = await WindowHelpers.CreateInvisibleWindowAsync<NumericUpDownWindow>().ConfigureAwait(false);
+
+            this.textBox = this.window.TheNUD.FindChild<TextBox>();
+            this.numUp = this.window.TheNUD.FindChild<RepeatButton>("PART_NumericUp");
+            this.numDown = this.window.TheNUD.FindChild<RepeatButton>("PART_NumericDown");
+        }
+
+        /// <summary>
+        /// Called when an object is no longer needed. Called just before <see cref="M:System.IDisposable.Dispose" />
+        /// if the class also implements that.
+        /// </summary>
+        public Task DisposeAsync()
+        {
+            return Task.CompletedTask;
+        }
+
         public static bool NearlyEqual(double a, double b, double epsilon)
         {
             double absA = Math.Abs(a);
@@ -42,32 +69,22 @@ public static bool NearlyEqual(double a, double b, double epsilon)
         public async Task ShouldConvertTextInputWithSnapToMultipleOfInterval()
         {
             await TestHost.SwitchToAppThread();
-            var window = await WindowHelpers.CreateInvisibleWindowAsync<NumericUpDownWindow>().ConfigureAwait(false);
-            await TestHost.SwitchToAppThread();
-
-            var textBox = window.TheNUD.FindChild<TextBox>(string.Empty);
-            Assert.NotNull(textBox);
 
-            var numUp = window.TheNUD.FindChild<RepeatButton>("PART_NumericUp");
-            Assert.NotNull(numUp);
-            var numDown = window.TheNUD.FindChild<RepeatButton>("PART_NumericDown");
-            Assert.NotNull(numDown);
+            this.window.TheNUD.Interval = 0.1;
+            this.window.TheNUD.SnapToMultipleOfInterval = true;
 
-            window.TheNUD.Interval = 0.1;
-            window.TheNUD.SnapToMultipleOfInterval = true;
-
-            window.TheNUD.Value = 0;
+            this.window.TheNUD.Value = 0;
             for (int i = 1; i < 15; i++)
             {
                 numUp.RaiseEvent(new RoutedEventArgs(ButtonBase.ClickEvent));
-                Assert.Equal(0d + 0.1 * i, window.TheNUD.Value);
+                Assert.Equal(0d + 0.1 * i, this.window.TheNUD.Value);
             }
 
-            window.TheNUD.Value = 0;
+            this.window.TheNUD.Value = 0;
             for (int i = 1; i < 15; i++)
             {
                 numDown.RaiseEvent(new RoutedEventArgs(ButtonBase.ClickEvent));
-                Assert.Equal(0d - 0.1 * i, window.TheNUD.Value);
+                Assert.Equal(0d - 0.1 * i, this.window.TheNUD.Value);
             }
         }
 
@@ -76,28 +93,23 @@ public async Task ShouldConvertTextInputWithSnapToMultipleOfInterval()
         public async Task ShouldConvertTextInput()
         {
             await TestHost.SwitchToAppThread();
-            var window = await WindowHelpers.CreateInvisibleWindowAsync<NumericUpDownWindow>().ConfigureAwait(false);
-            await TestHost.SwitchToAppThread();
-
-            var textBox = window.TheNUD.FindChild<TextBox>(string.Empty);
-            Assert.NotNull(textBox);
 
-            window.TheNUD.NumericInputMode = NumericInput.All;
+            this.window.TheNUD.NumericInputMode = NumericInput.All;
 
             SetText(textBox, "42");
-            Assert.Equal(42d, window.TheNUD.Value);
+            Assert.Equal(42d, this.window.TheNUD.Value);
 
             SetText(textBox, "42.2");
-            Assert.Equal(42.2d, window.TheNUD.Value);
+            Assert.Equal(42.2d, this.window.TheNUD.Value);
 
             SetText(textBox, ".");
-            Assert.Equal(0d, window.TheNUD.Value);
+            Assert.Equal(0d, this.window.TheNUD.Value);
 
             SetText(textBox, ".9");
-            Assert.Equal(0.9d, window.TheNUD.Value);
+            Assert.Equal(0.9d, this.window.TheNUD.Value);
 
             SetText(textBox, ".0115");
-            Assert.Equal(0.0115d, window.TheNUD.Value);
+            Assert.Equal(0.0115d, this.window.TheNUD.Value);
         }
 
         [Fact]
@@ -105,55 +117,50 @@ public async Task ShouldConvertTextInput()
         public async Task ShouldConvertTextInputWithStringFormat()
         {
             await TestHost.SwitchToAppThread();
-            var window = await WindowHelpers.CreateInvisibleWindowAsync<NumericUpDownWindow>().ConfigureAwait(false);
-            await TestHost.SwitchToAppThread();
-
-            var textBox = window.TheNUD.FindChild<TextBox>(string.Empty);
-            Assert.NotNull(textBox);
 
-            window.TheNUD.NumericInputMode = NumericInput.All;
-            window.TheNUD.StringFormat = "{}{0:N2} cm";
+            this.window.TheNUD.NumericInputMode = NumericInput.All;
+            this.window.TheNUD.StringFormat = "{}{0:N2} cm";
 
             SetText(textBox, "42");
-            Assert.Equal(42d, window.TheNUD.Value);
+            Assert.Equal(42d, this.window.TheNUD.Value);
             Assert.Equal("42.00 cm", textBox.Text);
 
             SetText(textBox, "42.2");
-            Assert.Equal(42.2d, window.TheNUD.Value);
+            Assert.Equal(42.2d, this.window.TheNUD.Value);
             Assert.Equal("42.20 cm", textBox.Text);
 
             SetText(textBox, ".");
-            Assert.Equal(0d, window.TheNUD.Value);
+            Assert.Equal(0d, this.window.TheNUD.Value);
             Assert.Equal("0.00 cm", textBox.Text);
 
             SetText(textBox, ".9");
-            Assert.Equal(0.9d, window.TheNUD.Value);
+            Assert.Equal(0.9d, this.window.TheNUD.Value);
             Assert.Equal("0.90 cm", textBox.Text);
 
             SetText(textBox, ".0115");
-            Assert.Equal(0.0115d, window.TheNUD.Value);
+            Assert.Equal(0.0115d, this.window.TheNUD.Value);
             Assert.Equal("0.01 cm", textBox.Text);
 
             SetText(textBox, ".0155");
-            Assert.Equal(0.0155d, window.TheNUD.Value);
+            Assert.Equal(0.0155d, this.window.TheNUD.Value);
             Assert.Equal("0.02 cm", textBox.Text);
 
             SetText(textBox, "100.00 cm");
-            Assert.Equal(100d, window.TheNUD.Value);
+            Assert.Equal(100d, this.window.TheNUD.Value);
             Assert.Equal("100.00 cm", textBox.Text);
 
             SetText(textBox, "200.00cm");
-            Assert.Equal(200d, window.TheNUD.Value);
+            Assert.Equal(200d, this.window.TheNUD.Value);
             Assert.Equal("200.00 cm", textBox.Text);
 
             SetText(textBox, "200.00");
-            Assert.Equal(200d, window.TheNUD.Value);
+            Assert.Equal(200d, this.window.TheNUD.Value);
             Assert.Equal("200.00 cm", textBox.Text);
 
             // GH-3551
-            window.TheNUD.StringFormat = "{}{0}mmHg";
+            this.window.TheNUD.StringFormat = "{}{0}mmHg";
             SetText(textBox, "15");
-            Assert.Equal(15, window.TheNUD.Value);
+            Assert.Equal(15, this.window.TheNUD.Value);
             Assert.Equal("15mmHg", textBox.Text);
         }
 
@@ -162,117 +169,112 @@ public async Task ShouldConvertTextInputWithStringFormat()
         public async Task ShouldConvertTextInputWithPercentStringFormat()
         {
             await TestHost.SwitchToAppThread();
-            var window = await WindowHelpers.CreateInvisibleWindowAsync<NumericUpDownWindow>().ConfigureAwait(false);
-            await TestHost.SwitchToAppThread();
-
-            var textBox = window.TheNUD.FindChild<TextBox>(string.Empty);
-            Assert.NotNull(textBox);
 
-            window.TheNUD.NumericInputMode = NumericInput.All;
+            this.window.TheNUD.NumericInputMode = NumericInput.All;
 
-            window.TheNUD.Culture = CultureInfo.GetCultureInfo("en-EN");
+            this.window.TheNUD.Culture = CultureInfo.GetCultureInfo("en-EN");
 
-            window.TheNUD.StringFormat = "{}{0:P0}";
+            this.window.TheNUD.StringFormat = "{}{0:P0}";
             SetText(textBox, "100");
-            Assert.Equal(1d, window.TheNUD.Value);
+            Assert.Equal(1d, this.window.TheNUD.Value);
             Assert.Equal("100%", textBox.Text);
 
             SetText(textBox, "100 %");
-            Assert.Equal(1d, window.TheNUD.Value);
+            Assert.Equal(1d, this.window.TheNUD.Value);
             Assert.Equal("100%", textBox.Text);
 
             SetText(textBox, "100%");
-            Assert.Equal(1d, window.TheNUD.Value);
+            Assert.Equal(1d, this.window.TheNUD.Value);
             Assert.Equal("100%", textBox.Text);
 
-            window.TheNUD.StringFormat = "{}{0:P1}";
+            this.window.TheNUD.StringFormat = "{}{0:P1}";
             SetText(textBox, "-0.39678");
-            Assert.True(NearlyEqual(-0.0039678d, window.TheNUD.Value.Value, 0.000005));
+            Assert.True(NearlyEqual(-0.0039678d, this.window.TheNUD.Value.Value, 0.000005));
             Assert.Equal("-0.4%", textBox.Text);
 
-            window.TheNUD.StringFormat = "{}{0:0%}";
+            this.window.TheNUD.StringFormat = "{}{0:0%}";
             SetText(textBox, "100%");
-            Assert.Equal(1d, window.TheNUD.Value);
+            Assert.Equal(1d, this.window.TheNUD.Value);
             Assert.Equal("100%", textBox.Text);
 
-            window.TheNUD.StringFormat = "P0";
+            this.window.TheNUD.StringFormat = "P0";
             SetText(textBox, "50");
-            Assert.Equal(0.5d, window.TheNUD.Value);
+            Assert.Equal(0.5d, this.window.TheNUD.Value);
             Assert.Equal("50%", textBox.Text);
 
-            window.TheNUD.StringFormat = "P1";
+            this.window.TheNUD.StringFormat = "P1";
             SetText(textBox, "-0.39678");
-            Assert.True(NearlyEqual(-0.0039678d, window.TheNUD.Value.Value, 0.000005));
+            Assert.True(NearlyEqual(-0.0039678d, this.window.TheNUD.Value.Value, 0.000005));
             Assert.Equal("-0.4%", textBox.Text);
 
-            window.TheNUD.Culture = CultureInfo.InvariantCulture;
+            this.window.TheNUD.Culture = CultureInfo.InvariantCulture;
 
-            window.TheNUD.StringFormat = "{}{0:P0}";
+            this.window.TheNUD.StringFormat = "{}{0:P0}";
             SetText(textBox, "10");
-            Assert.Equal(0.1d, window.TheNUD.Value);
+            Assert.Equal(0.1d, this.window.TheNUD.Value);
             Assert.Equal("10 %", textBox.Text);
 
-            window.TheNUD.StringFormat = "{}{0:P1}";
+            this.window.TheNUD.StringFormat = "{}{0:P1}";
             SetText(textBox, "-0.39678");
-            Assert.True(NearlyEqual(-0.0039678d, window.TheNUD.Value.Value, 0.000005));
+            Assert.True(NearlyEqual(-0.0039678d, this.window.TheNUD.Value.Value, 0.000005));
             Assert.Equal("-0.4 %", textBox.Text);
 
-            window.TheNUD.StringFormat = "P0";
+            this.window.TheNUD.StringFormat = "P0";
             SetText(textBox, "1");
-            Assert.Equal(0.01d, window.TheNUD.Value);
+            Assert.Equal(0.01d, this.window.TheNUD.Value);
             Assert.Equal("1 %", textBox.Text);
 
-            window.TheNUD.StringFormat = "P1";
+            this.window.TheNUD.StringFormat = "P1";
             SetText(textBox, "-0.39678");
-            Assert.True(NearlyEqual(-0.0039678d, window.TheNUD.Value.Value, 0.000005));
+            Assert.True(NearlyEqual(-0.0039678d, this.window.TheNUD.Value.Value, 0.000005));
             Assert.Equal("-0.4 %", textBox.Text);
 
-            window.TheNUD.StringFormat = "{}{0:0.0%}";
+            this.window.TheNUD.StringFormat = "{}{0:0.0%}";
             SetText(textBox, "1");
-            Assert.Equal(0.01d, window.TheNUD.Value);
+            Assert.Equal(0.01d, this.window.TheNUD.Value);
             Assert.Equal("1.0%", textBox.Text);
 
-            window.TheNUD.StringFormat = "{0:0.0%}";
+            this.window.TheNUD.StringFormat = "{0:0.0%}";
             SetText(textBox, "1");
-            Assert.Equal(0.01d, window.TheNUD.Value);
+            Assert.Equal(0.01d, this.window.TheNUD.Value);
             Assert.Equal("1.0%", textBox.Text);
 
-            window.TheNUD.StringFormat = "0.0%";
+            this.window.TheNUD.StringFormat = "0.0%";
             SetText(textBox, "1");
-            Assert.Equal(0.01d, window.TheNUD.Value);
-            Assert.Equal("1.0%", textBox.Text);            
+            Assert.Equal(0.01d, this.window.TheNUD.Value);
+            Assert.Equal("1.0%", textBox.Text);
 
-            window.TheNUD.StringFormat = "{}{0:0.0‰}";
+            this.window.TheNUD.StringFormat = "{}{0:0.0‰}";
             SetText(textBox, "1");
-            Assert.Equal(0.001d, window.TheNUD.Value);
+            Assert.Equal(0.001d, this.window.TheNUD.Value);
             Assert.Equal("1.0‰", textBox.Text);
 
-            window.TheNUD.StringFormat = "{0:0.0‰}";
+            this.window.TheNUD.StringFormat = "{0:0.0‰}";
             SetText(textBox, "1");
-            Assert.Equal(0.001d, window.TheNUD.Value);
+            Assert.Equal(0.001d, this.window.TheNUD.Value);
             Assert.Equal("1.0‰", textBox.Text);
 
-            window.TheNUD.StringFormat = "0.0‰";
+            this.window.TheNUD.StringFormat = "0.0‰";
             SetText(textBox, "1");
-            Assert.Equal(0.001d, window.TheNUD.Value);
+            Assert.Equal(0.001d, this.window.TheNUD.Value);
             Assert.Equal("1.0‰", textBox.Text);
 
             // GH-3376 Case 3
-            window.TheNUD.StringFormat = "{0:0.0000}%";
+            this.window.TheNUD.StringFormat = "{0:0.0000}%";
             SetText(textBox, "0.25");
-            Assert.Equal(0.25d, window.TheNUD.Value);
+            Assert.Equal(0.25d, this.window.TheNUD.Value);
             Assert.Equal("0.2500%", textBox.Text);
 
             // GH-3376 Case 4
-            window.TheNUD.StringFormat = "{0:0.0000}‰";
+            this.window.TheNUD.StringFormat = "{0:0.0000}‰";
             SetText(textBox, "0.25");
-            Assert.Equal(0.25d, window.TheNUD.Value);
+            Assert.Equal(0.25d, this.window.TheNUD.Value);
             Assert.Equal("0.2500‰", textBox.Text);
 
             // GH-3376#issuecomment-472324787
-            window.TheNUD.StringFormat = "{}{0:G3} mPa·s";
+            this.window.TheNUD.StringFormat = "{}{0:G3} mPa·s";
             SetText(textBox, "0.986");
-            Assert.Equal(0.986d, window.TheNUD.Value);
+            Assert.Equal(0.986d, this.window.TheNUD.Value);
             Assert.Equal("0.986 mPa·s", textBox.Text);
         }
 
@@ -281,28 +283,23 @@ public async Task ShouldConvertTextInputWithPercentStringFormat()
         public async Task ShouldConvertDecimalTextInput()
         {
             await TestHost.SwitchToAppThread();
-            var window = await WindowHelpers.CreateInvisibleWindowAsync<NumericUpDownWindow>().ConfigureAwait(false);
-            await TestHost.SwitchToAppThread();
-
-            var textBox = window.TheNUD.FindChild<TextBox>(string.Empty);
-            Assert.NotNull(textBox);
 
-            window.TheNUD.NumericInputMode = NumericInput.Decimal;
+            this.window.TheNUD.NumericInputMode = NumericInput.Decimal;
 
             SetText(textBox, "42");
-            Assert.Equal(42d, window.TheNUD.Value);
+            Assert.Equal(42d, this.window.TheNUD.Value);
 
             SetText(textBox, "42.2");
-            Assert.Equal(42.2d, window.TheNUD.Value);
+            Assert.Equal(42.2d, this.window.TheNUD.Value);
 
             SetText(textBox, ".");
-            Assert.Equal(0d, window.TheNUD.Value);
+            Assert.Equal(0d, this.window.TheNUD.Value);
 
             SetText(textBox, ".9");
-            Assert.Equal(0.9d, window.TheNUD.Value);
+            Assert.Equal(0.9d, this.window.TheNUD.Value);
 
             SetText(textBox, ".0115");
-            Assert.Equal(0.0115d, window.TheNUD.Value);
+            Assert.Equal(0.0115d, this.window.TheNUD.Value);
         }
 
         [Fact]
@@ -310,30 +307,25 @@ public async Task ShouldConvertDecimalTextInput()
         public async Task ShouldConvertDecimalTextInputWithSpecialCulture()
         {
             await TestHost.SwitchToAppThread();
-            var window = await WindowHelpers.CreateInvisibleWindowAsync<NumericUpDownWindow>().ConfigureAwait(false);
-            await TestHost.SwitchToAppThread();
-
-            var textBox = window.TheNUD.FindChild<TextBox>(string.Empty);
-            Assert.NotNull(textBox);
 
-            window.TheNUD.NumericInputMode = NumericInput.Decimal;
+            this.window.TheNUD.NumericInputMode = NumericInput.Decimal;
 
-            window.TheNUD.Culture = CultureInfo.GetCultureInfo("fa-IR");
+            this.window.TheNUD.Culture = CultureInfo.GetCultureInfo("fa-IR");
 
             SetText(textBox, "42");
-            Assert.Equal(42d, window.TheNUD.Value);
+            Assert.Equal(42d, this.window.TheNUD.Value);
 
             SetText(textBox, "42/751");
-            Assert.Equal(42.751d, window.TheNUD.Value);
+            Assert.Equal(42.751d, this.window.TheNUD.Value);
 
             SetText(textBox, "/");
-            Assert.Equal(0d, window.TheNUD.Value);
+            Assert.Equal(0d, this.window.TheNUD.Value);
 
             SetText(textBox, "/9");
-            Assert.Equal(0.9d, window.TheNUD.Value);
+            Assert.Equal(0.9d, this.window.TheNUD.Value);
 
             SetText(textBox, "/0115");
-            Assert.Equal(0.0115d, window.TheNUD.Value);
+            Assert.Equal(0.0115d, this.window.TheNUD.Value);
         }
 
         [Fact]
@@ -341,25 +333,20 @@ public async Task ShouldConvertDecimalTextInputWithSpecialCulture()
         public async Task ShouldConvertNumericTextInput()
         {
             await TestHost.SwitchToAppThread();
-            var window = await WindowHelpers.CreateInvisibleWindowAsync<NumericUpDownWindow>().ConfigureAwait(false);
-            await TestHost.SwitchToAppThread();
 
-            var textBox = window.TheNUD.FindChild<TextBox>(string.Empty);
-            Assert.NotNull(textBox);
-
-            window.TheNUD.NumericInputMode = NumericInput.Numbers;
+            this.window.TheNUD.NumericInputMode = NumericInput.Numbers;
 
             SetText(textBox, "42");
-            Assert.Equal(42d, window.TheNUD.Value);
+            Assert.Equal(42d, this.window.TheNUD.Value);
 
             SetText(textBox, "42.2");
-            Assert.Null(window.TheNUD.Value);
+            Assert.Null(this.window.TheNUD.Value);
 
             SetText(textBox, ".");
-            Assert.Null(window.TheNUD.Value);
+            Assert.Null(this.window.TheNUD.Value);
 
             SetText(textBox, ".9");
-            Assert.Null(window.TheNUD.Value);
+            Assert.Null(this.window.TheNUD.Value);
         }
 
         [Fact]
@@ -367,46 +354,41 @@ public async Task ShouldConvertNumericTextInput()
         public async Task ShouldConvertHexadecimalTextInput()
         {
             await TestHost.SwitchToAppThread();
-            var window = await WindowHelpers.CreateInvisibleWindowAsync<NumericUpDownWindow>().ConfigureAwait(false);
-            await TestHost.SwitchToAppThread();
-
-            var textBox = window.TheNUD.FindChild<TextBox>(string.Empty);
-            Assert.NotNull(textBox);
 
-            window.TheNUD.NumericInputMode = NumericInput.Numbers;
-            window.TheNUD.ParsingNumberStyle = NumberStyles.HexNumber;
+            this.window.TheNUD.NumericInputMode = NumericInput.Numbers;
+            this.window.TheNUD.ParsingNumberStyle = NumberStyles.HexNumber;
 
             SetText(textBox, "F");
-            Assert.Equal(15d, window.TheNUD.Value);
+            Assert.Equal(15d, this.window.TheNUD.Value);
 
             SetText(textBox, "1F");
-            Assert.Equal(31d, window.TheNUD.Value);
+            Assert.Equal(31d, this.window.TheNUD.Value);
 
             SetText(textBox, "37C5");
-            Assert.Equal(14277d, window.TheNUD.Value);
+            Assert.Equal(14277d, this.window.TheNUD.Value);
 
             SetText(textBox, "ACDC");
-            Assert.Equal(44252d, window.TheNUD.Value);
+            Assert.Equal(44252d, this.window.TheNUD.Value);
 
             SetText(textBox, "10000");
-            Assert.Equal(65536d, window.TheNUD.Value);
+            Assert.Equal(65536d, this.window.TheNUD.Value);
 
             SetText(textBox, "AFFE");
-            Assert.Equal(45054d, window.TheNUD.Value);
+            Assert.Equal(45054d, this.window.TheNUD.Value);
 
             SetText(textBox, "AFFE0815");
-            Assert.Equal(2952661013d, window.TheNUD.Value);
+            Assert.Equal(2952661013d, this.window.TheNUD.Value);
         }
 
         private static void SetText(TextBox textBox, string text)
         {
             textBox.Clear();
             var textCompositionEventArgs = new TextCompositionEventArgs(Keyboard.PrimaryDevice, new TextComposition(InputManager.Current, textBox, text));
-            textCompositionEventArgs.RoutedEvent = TextBox.PreviewTextInputEvent;
+            textCompositionEventArgs.RoutedEvent = UIElement.PreviewTextInputEvent;
             textBox.RaiseEvent(textCompositionEventArgs);
-            textCompositionEventArgs.RoutedEvent = TextBox.TextInputEvent;
+            textCompositionEventArgs.RoutedEvent = UIElement.TextInputEvent;
             textBox.RaiseEvent(textCompositionEventArgs);
-            textBox.RaiseEvent(new RoutedEventArgs(TextBox.LostFocusEvent));
+            textBox.RaiseEvent(new RoutedEventArgs(UIElement.LostFocusEvent));
         }
     }
 }
\ No newline at end of file