fixed unix file move (#701)

Co-authored-by: Flepp Jann <JFlepp@Hamilton.ch>
Co-authored-by: Florian Greinacher <florian@greinacher.de>

Author: 3 people

src/System.IO.Abstractions.TestingHelpers/MockFileSystem.cs

@@ -248,7 +248,7 @@ public void MoveDirectory(string sourcePath, string destPath)
 
                 foreach (var path in affectedPaths)
                 {
-                    var newPath = StringOperations.Replace(path, sourcePath, destPath);
+                    var newPath = Path.Combine(destPath, path.Substring(sourcePath.Length).TrimStart(Path.DirectorySeparatorChar));
                     var entry = files[path];
                     entry.Path = newPath;
                     files[newPath] = entry;

tests/System.IO.Abstractions.TestingHelpers.Tests/MockFileSystemTests.cs

@@ -252,6 +252,18 @@ public void MockFileSystem_AddFilesFromEmbeddedResource_ShouldAddAllTheFiles()
             Assert.Contains(XFS.Path(@"C:\SecondTestFile.txt"), fileSystem.AllFiles.ToList());
         }
 
+        [Test]
+        public void MockFileSystem_MoveDirectory_MovesDirectoryWithoutRenamingFiles()
+        {
+            var fileSystem = new MockFileSystem();
+            fileSystem.AddFile(XFS.Path(@"C:\dir1\dir1\dir1.txt"), string.Empty);
+
+            fileSystem.MoveDirectory(XFS.Path(@"C:\dir1"), XFS.Path(@"C:\dir2"));
+
+            var expected = new[] { XFS.Path(@"C:\dir2\dir1\dir1.txt") };
+            CollectionAssert.AreEquivalent(expected, fileSystem.AllFiles);
+        }
+
         [Test]
         public void MockFileSystem_MoveDirectoryAndFile_ShouldMoveCorrectly()
         {