diff --git a/Tests/JustAssembly.Tests/FileValidatorTests.cs b/Tests/JustAssembly.Tests/FileValidatorTests.cs
new file mode 100644
index 0000000..6c481a0
--- /dev/null
+++ b/Tests/JustAssembly.Tests/FileValidatorTests.cs
@@ -0,0 +1,48 @@
+
+using System;
+using System.IO;
+using JustAssembly.CommandLineTool;
+using NUnit.Framework;
+
+namespace JustAssembly.Tests
+{
+    [TestFixture]
+    public class FileValidatorTests
+    {
+        [TestCase]
+        public void ExtensionsMustBeValid()
+        {
+            var fullFilename = EnsureFileExists("SomeFile.xml");
+
+            Assert.False(FilePathValidater.ValidateInputFile(fullFilename),"xml extension should not be accepted as valid");
+        }
+
+
+        [TestCase]
+        public void HappyCase()
+        {
+            var fullFileName =EnsureFileExists("SomeFile.dll");
+            Assert.True(FilePathValidater.ValidateInputFile(fullFileName),"dll should have been accepted");
+        }
+
+        [TestCase]
+        public void HappyCase_RegardlessExtensionCasing()
+        {
+            var fullFileName =EnsureFileExists("SomeFile.DLL");
+            Assert.True(FilePathValidater.ValidateInputFile(fullFileName),"dll should have been accepted");
+        }
+
+
+
+
+        private static string EnsureFileExists(string fileName)
+        {
+            var tempFolder = Path.GetTempPath();
+            var folderName = Guid.NewGuid().ToString();
+            var newFolder = Directory.CreateDirectory(folderName);
+            var fullFilename = Path.Combine(newFolder.FullName, fileName);
+            File.WriteAllText(fullFilename, string.Empty);
+            return fullFilename;
+        }
+    }
+}
diff --git a/Tests/JustAssembly.Tests/JustAssembly.Tests.csproj b/Tests/JustAssembly.Tests/JustAssembly.Tests.csproj
index 85aea10..a247883 100644
--- a/Tests/JustAssembly.Tests/JustAssembly.Tests.csproj
+++ b/Tests/JustAssembly.Tests/JustAssembly.Tests.csproj
@@ -59,6 +59,7 @@
     </Compile>
     <Compile Include="APIDiff\BaseExistingAPIDiffTestFixture.cs" />
     <Compile Include="APIDiff\ExistingAPIDiffTestFixture.cs" />
+    <Compile Include="FileValidatorTests.cs" />
     <Compile Include="SimpleTestClass.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
   </ItemGroup>
@@ -71,6 +72,10 @@
       <Project>{d68133bd-1e63-496e-9ede-4fbdbf77b486}</Project>
       <Name>Mono.Cecil</Name>
     </ProjectReference>
+    <ProjectReference Include="..\..\UI\JustAssembly.CommandLineTool\JustAssembly.CommandLineTool.csproj">
+      <Project>{C6D6187D-CB83-40A1-A3F6-20FB9231D67B}</Project>
+      <Name>JustAssembly.CommandLineTool</Name>
+    </ProjectReference>
   </ItemGroup>
   <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
diff --git a/UI/JustAssembly.CommandLineTool/FilePathValidater.cs b/UI/JustAssembly.CommandLineTool/FilePathValidater.cs
index ae4a349..204e3e9 100644
--- a/UI/JustAssembly.CommandLineTool/FilePathValidater.cs
+++ b/UI/JustAssembly.CommandLineTool/FilePathValidater.cs
@@ -1,5 +1,7 @@
-using System.Collections.Generic;
+using System;
+using System.Collections.Generic;
 using System.IO;
+using System.Linq;
 
 namespace JustAssembly.CommandLineTool
 {
@@ -27,12 +29,7 @@ private static bool ValidateFile(string filePath, List<string> validExtensions)
             }
 
             string extension = Path.GetExtension(filePath);
-            if (!validExtensions.Contains(extension))
-            {
-                return false;
-            }
-
-            return true;
+            return validExtensions.Any(x =>  x.Equals(extension,StringComparison.CurrentCultureIgnoreCase));
         }
     }
 }
diff --git a/UI/JustAssembly.CommandLineTool/Properties/AssemblyInfo.cs b/UI/JustAssembly.CommandLineTool/Properties/AssemblyInfo.cs
index bcf4371..605f41c 100644
--- a/UI/JustAssembly.CommandLineTool/Properties/AssemblyInfo.cs
+++ b/UI/JustAssembly.CommandLineTool/Properties/AssemblyInfo.cs
@@ -18,3 +18,4 @@
 
 // The following GUID is for the ID of the typelib if this project is exposed to COM
 [assembly: Guid("c6d6187d-cb83-40a1-a3f6-20fb9231d67b")]
+[assembly:InternalsVisibleTo("JustAssembly.Tests")]