Ensure MockFile.Copy clones contents (#354)

* Ensure MockFile.Copy clones contents

Fixes #353

* Adapt formatting

Author: fgreinacher

System.IO.Abstractions.TestingHelpers.Tests/MockFileCopyTests.cs

@@ -27,6 +27,27 @@ public void MockFile_Copy_ShouldOverwriteFileWhenOverwriteFlagIsTrue()
             Assert.AreEqual(copyResult.Contents, sourceContents.Contents);
         }
 
+        [Test]
+        public void MockFile_Copy_ShouldCloneContents()
+        {
+            var sourceFileName = XFS.Path(@"c:\source\demo.txt");
+            var destFileName = XFS.Path(@"c:\source\demo_copy.txt");
+
+            var mockFileSystem = new MockFileSystem();
+            mockFileSystem.AddFile(sourceFileName, "Original");
+            mockFileSystem.File.Copy(sourceFileName, destFileName);
+            
+            using (var stream = mockFileSystem.File.Open(sourceFileName, FileMode.Open, FileAccess.ReadWrite))
+            {
+                var binaryWriter = new System.IO.BinaryWriter(stream);
+
+                binaryWriter.Seek(0, SeekOrigin.Begin);
+                binaryWriter.Write("Modified");
+            }
+
+            Assert.AreEqual("Original", mockFileSystem.File.ReadAllText(destFileName));
+        }
+
         [Test]
         public void MockFile_Copy_ShouldCreateFileAtNewDestination()
         {

System.IO.Abstractions.TestingHelpers/MockFile.cs

@@ -129,8 +129,8 @@ public override void Copy(string sourceFileName, string destFileName, bool overw
                 mockFileDataAccessor.RemoveFile(destFileName);
             }
 
-            var sourceFile = mockFileDataAccessor.GetFile(sourceFileName);
-            mockFileDataAccessor.AddFile(destFileName, sourceFile);
+            var sourceFileData = mockFileDataAccessor.GetFile(sourceFileName);
+            mockFileDataAccessor.AddFile(destFileName, new MockFileData(sourceFileData));
         }
 
         public override Stream Create(string path)

System.IO.Abstractions.TestingHelpers/MockFileData.cs

@@ -81,6 +81,27 @@ public MockFileData(byte[] contents)
             Contents = contents ?? throw new ArgumentNullException(nameof(contents));
         }
 
+
+        /// <summary>
+        /// Initializes a new instance of the <see cref="MockFileData"/> class by copying the given <see cref="MockFileData"/>.
+        /// </summary>
+        /// <param name="template">The template instance.</param>
+        /// <exception cref="ArgumentNullException">Thrown if <paramref name="template"/> is <see langword="null" />.</exception>
+        public MockFileData(MockFileData template)
+        {
+            if (template == null)
+            {
+                throw new ArgumentNullException(nameof(template));
+            }
+
+            accessControl = template.accessControl;
+            Attributes = template.Attributes;
+            TextContents = template.TextContents;
+            CreationTime = template.CreationTime;
+            LastAccessTime = template.LastAccessTime;
+            LastWriteTime = template.LastWriteTime;
+        }
+
         /// <summary>
         /// Gets or sets the byte contents of the <see cref="MockFileData"/>.
         /// </summary>
@@ -141,4 +162,4 @@ public FileSecurity AccessControl
             set { accessControl = value; }
         }
     }
-}
+}