@@ -74,6 +74,7 @@
     </Reference>
   </ItemGroup>
   <ItemGroup>
+    <Compile Include="LineReplacer.cs" />
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="ReferenceVisitorTests.cs" />
   </ItemGroup>
 
@@ -0,0 +1,33 @@
+using System;
+using System.IO;
+using MbUnit.Framework;
+
+namespace CassetteHelperTests
+{
+    [TestFixture]
+    public class LineReplacerTests
+    {
+        [Test, ExpectedException(typeof(FileNotFoundException))]
+        public void IfFileDoesNotExistThrowsFileNotFoundException()
+        {
+            new LineReplacer("test.js");
+        }
+
+        [Test, ExpectedArgumentNullException("filePath")]
+        [Row("")]
+        [Row(null)]
+        public void NullOrEmptyFilePathThrowsArgumentNullException(string filePath)
+        {
+            new LineReplacer(filePath);
+        }
+    }
+
+    public class LineReplacer
+    {
+        public LineReplacer(string filePath)
+        {
+            if (string.IsNullOrEmpty(filePath)) throw new ArgumentNullException("filePath");
+            if(!File.Exists(filePath)) throw new FileNotFoundException("Could not find file to replace lines in", filePath);
+        }
+    }
+}
@@ -0,0 +1,33 @@
+using System;
+using System.IO;
+using MbUnit.Framework;
+
+namespace CassetteHelperTests
+{
+    [TestFixture]
+    public class LineReplacerTests
+    {
+        [Test, ExpectedException(typeof(FileNotFoundException))]
+        public void IfFileDoesNotExistThrowsFileNotFoundException()
+        {
+            new LineReplacer("test.js");
+        }
+
+        [Test, ExpectedArgumentNullException("filePath")]
+        [Row("")]
+        [Row(null)]
+        public void NullOrEmptyFilePathThrowsArgumentNullException(string filePath)
+        {
+            new LineReplacer(filePath);
+        }
+    }
+
+    public class LineReplacer
+    {
+        public LineReplacer(string filePath)
+        {
+            if (string.IsNullOrEmpty(filePath)) throw new ArgumentNullException("filePath");
+            if(!File.Exists(filePath)) throw new FileNotFoundException("Could not find file to replace lines in", filePath);
+        }
+    }
+}