From 03aa8ca0c5c4f0c0de5902dce36d626aa68fba2e Mon Sep 17 00:00:00 2001
From: Sutikshan Dubey <sutikshan.dubey@adp.com>
Date: Wed, 20 Nov 2013 15:17:51 +0530
Subject: [PATCH] Added MockFile.AppendText Implementation with unit test.

---
 TestHelpers.Tests/MockFileTests.cs         | 35 ++++++++++++++++++++++
 TestHelpers.Tests/TestHelpers.Tests.csproj |  3 ++
 TestingHelpers/MockFile.cs                 | 12 +++++++-
 3 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/TestHelpers.Tests/MockFileTests.cs b/TestHelpers.Tests/MockFileTests.cs
index 402f9acb6..3c6f581f7 100644
--- a/TestHelpers.Tests/MockFileTests.cs
+++ b/TestHelpers.Tests/MockFileTests.cs
@@ -1154,5 +1154,40 @@ public void MockFile_Open_OverwritesExistingFileOnCreate()
             Assert.That(stream.Length, Is.EqualTo(0));
             Assert.That(file.Contents.Length, Is.EqualTo(0));
         }
+        [Test]
+        public void MockFile_AppendText_AppendTextToanExistingFile()
+        {
+            const string filepath = @"c:\something\does\exist.txt";
+            var filesystem = new MockFileSystem(new Dictionary<string, MockFileData>
+            {
+                { filepath, new MockFileData("I'm here. ") }
+            });
+
+            var stream = filesystem.File.AppendText(filepath);
+
+            stream.Write("Me too!");
+            stream.Flush();
+            stream.Close();
+
+            var file = filesystem.GetFile(filepath);
+            Assert.That(file.TextContents, Is.EqualTo("I'm here. Me too!"));
+        }
+
+        [Test]
+        public void MockFile_AppendText_CreatesNewFileForAppendToNonExistingFile()
+        {
+            const string filepath = @"c:\something\doesnt\exist.txt";
+            var filesystem = new MockFileSystem(new Dictionary<string, MockFileData>());
+
+            var stream = filesystem.File.AppendText(filepath);
+
+            stream.Write("New too!");
+            stream.Flush();
+            stream.Close();
+
+            var file = filesystem.GetFile(filepath);
+            Assert.That(file.TextContents, Is.EqualTo("New too!"));
+            Assert.That(filesystem.FileExists(filepath));
+        }
     }
 }
\ No newline at end of file
diff --git a/TestHelpers.Tests/TestHelpers.Tests.csproj b/TestHelpers.Tests/TestHelpers.Tests.csproj
index 3e28fe4f7..d4e9bff74 100644
--- a/TestHelpers.Tests/TestHelpers.Tests.csproj
+++ b/TestHelpers.Tests/TestHelpers.Tests.csproj
@@ -117,6 +117,9 @@
     <None Include="packages.config" />
     <Compile Include="StringExtensionsTests.cs" />
   </ItemGroup>
+  <ItemGroup>
+    <Service Include="{82A7F48D-3B50-4B1E-B82E-3ADA8210C358}" />
+  </ItemGroup>
   <Import Project="$(MSBuildBinPath)\Microsoft.CSharp.targets" />
   <Import Project="$(SolutionDir)\.nuget\nuget.targets" />
   <!-- To modify your build process, add your task inside one of the targets below and uncomment it. 
diff --git a/TestingHelpers/MockFile.cs b/TestingHelpers/MockFile.cs
index 5ffe1e65e..5bed838b0 100644
--- a/TestingHelpers/MockFile.cs
+++ b/TestingHelpers/MockFile.cs
@@ -33,7 +33,17 @@ public override void AppendAllText(string path, string contents, Encoding encodi
 
         public override StreamWriter AppendText(string path)
         {
-            throw new NotImplementedException("This test helper hasn't been implemented yet. They are implemented on an as-needed basis. As it seems like you need it, now would be a great time to send us a pull request over at https://github.com/tathamoddie/System.IO.Abstractions. You know, because it's open source and all.");
+            if (mockFileDataAccessor.FileExists(path))
+            {
+                StreamWriter sw = new StreamWriter(OpenWrite(path));
+                sw.BaseStream.Seek(0, SeekOrigin.End); //push the stream pointer at the end for append.
+                return sw;
+
+            }
+            else
+            {
+                return new StreamWriter(Create(path));
+            }
         }
 
         public override void Copy(string sourceFileName, string destFileName)