Clean up FirstCharacterToLower extension + tests

src/NzbDrone.Common.Test/ExtensionTests/StringExtensionTests/FirstCharacterToLowerFixture.cs

@@ -5,11 +5,13 @@ using NzbDrone.Common.Extensions;
 namespace NzbDrone.Common.Test.ExtensionTests.StringExtensionTests
 {
     [TestFixture]
-    public class FirstCharcacterToLowerFixture
+    public class FirstCharacterToLowerFixture
     {
         [TestCase("Hello", "hello")]
         [TestCase("CamelCase", "camelCase")]
         [TestCase("A Full Sentence", "a Full Sentence")]
+        [TestCase("", "")]
+        [TestCase(null, "")]
         public void should_lower_case_first_character(string input, string expected)
         {
             input.FirstCharToLower().Should().Be(expected);

src/NzbDrone.Common.Test/ExtensionTests/StringExtensionTests/FirstCharcacterToUpperFixture.cs

@@ -10,6 +10,8 @@ namespace NzbDrone.Common.Test.ExtensionTests.StringExtensionTests
         [TestCase("hello", "Hello")]
         [TestCase("camelCase", "CamelCase")]
         [TestCase("a full sentence", "A full sentence")]
+        [TestCase("", "")]
+        [TestCase(null, "")]
         public void should_capitalize_first_character(string input, string expected)
         {
             input.FirstCharToUpper().Should().Be(expected);

src/NzbDrone.Common.Test/NzbDrone.Common.Test.csproj

@@ -85,7 +85,7 @@
     <Compile Include="ExtensionTests\IEnumerableExtensionTests\IntersectByFixture.cs" />
     <Compile Include="ExtensionTests\Int64ExtensionFixture.cs" />
     <Compile Include="ExtensionTests\IPAddressExtensionsFixture.cs" />
-    <Compile Include="ExtensionTests\StringExtensionTests\FirstCharcacterToLowerFixture.cs" />
+    <Compile Include="ExtensionTests\StringExtensionTests\FirstCharacterToLowerFixture.cs" />
     <Compile Include="ExtensionTests\StringExtensionTests\FirstCharcacterToUpperFixture.cs" />
     <Compile Include="ExtensionTests\UrlExtensionsFixture.cs" />
     <Compile Include="HashUtilFixture.cs" />

src/NzbDrone.Common/Extensions/StringExtensions.cs

@@ -24,12 +24,22 @@ namespace NzbDrone.Common.Extensions
 
         public static string FirstCharToLower(this string input)
         {
-            return input.First().ToString().ToLower() + input.Substring(1);
+            if (string.IsNullOrEmpty(input))
+            {
+                return string.Empty;
+            }
+
+            return char.ToLowerInvariant(input.First()) + input.Substring(1);
         }
 
         public static string FirstCharToUpper(this string input)
         {
-            return input.First().ToString().ToUpper() + input.Substring(1);
+            if (string.IsNullOrEmpty(input))
+            {
+                return string.Empty;
+            }
+
+            return char.ToUpperInvariant(input.First()) + input.Substring(1);
         }
 
         public static string Inject(this string format, params object[] formattingArgs)