Add NumberToColorConverter tests

Tests/MVVM/Converters/NumberToColorConverterTests.cs

@@ -0,0 +1,47 @@
+// WatchOnlyBitcoinWallet Tests
+// Copyright (c) 2016 Coding Enthusiast
+// Distributed under the MIT software license, see the accompanying
+// file LICENCE or http://www.opensource.org/licenses/mit-license.php.
+
+using Avalonia.Media;
+using System.Globalization;
+using WatchOnlyBitcoinWallet.MVVM.Converters;
+
+namespace Tests.MVVM.Converters
+{
+    public class NumberToColorConverterTests
+    {
+        public static TheoryData<decimal, IImmutableSolidColorBrush> GetConvertCases()
+        {
+            TheoryData<decimal, IImmutableSolidColorBrush> result = new()
+            {
+                { 0, Brushes.Transparent },
+                { 0.01m, Brushes.LightGreen },
+                { -0.002m, Brushes.Orange },
+            };
+
+            return result;
+        }
+        [Theory]
+        [MemberData(nameof(GetConvertCases))]
+        public void ConvertTest(decimal value, IImmutableSolidColorBrush expected)
+        {
+            NumberToColorConverter converter = new();
+            object actual = converter.Convert(value, typeof(decimal), null, CultureInfo.InvariantCulture);
+            Assert.Equal(expected, actual);
+        }
+
+        [Fact]
+        public void ExceptionTests()
+        {
+            NumberToColorConverter converter = new();
+            Type t = typeof(decimal);
+            CultureInfo ci = CultureInfo.InvariantCulture;
+
+            Assert.Throws<NotImplementedException>(() => converter.Convert(null, t, null, ci));
+            Assert.Throws<NotImplementedException>(() => converter.Convert("foo", t, null, ci));
+            Assert.Throws<NotImplementedException>(() => converter.Convert(123, t, null, ci));
+            Assert.Throws<NotImplementedException>(() => converter.ConvertBack(null, t, null, ci));
+        }
+    }
+}

WatchOnlyBitcoinWallet/MVVM/Converters/NumberToColorConverter.cs

@@ -11,30 +11,31 @@ namespace WatchOnlyBitcoinWallet.MVVM.Converters
 {
     /// <summary>
     /// Converts a decimal number to color.
-    /// </para> positive : green
-    /// </para> negative : red
-    /// </para> zero : null
+    /// <para/> positive : green
+    /// <para/> negative : red
+    /// <para/> zero : transparent
     /// </summary>
     public class NumberToColorConverter : IValueConverter
     {
-        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+        public object Convert(object? value, Type targetType, object? parameter, System.Globalization.CultureInfo culture)
         {
-            decimal number = (decimal)value;
-            if (number == 0)
+            if (value is decimal d)
             {
-                return null;
-            }
-            else if (number >= 0)
-            {
-                return Brushes.LightGreen;
-            }
-            else
-            {
-                return Brushes.Orange;
+                switch (d)
+                {
+                    case 0:
+                        return Brushes.Transparent;
+                    case > 0:
+                        return Brushes.LightGreen;
+                    case < 0:
+                        return Brushes.Orange;
+                }
             }
+
+            throw new NotImplementedException();
         }
 
-        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
+        public object ConvertBack(object? value, Type targetType, object? parameter, System.Globalization.CultureInfo culture)
         {
             throw new NotImplementedException();
         }