Fix Unit Tests

Author: Simon Ensslen

src/ICSharpCode.SharpZipLib/Tar/TarStringExtension.cs

@@ -6,9 +6,10 @@ internal static class TarStringExtension
 	{
 		public static string ClearTarPath(this string s)
 		{
-			if (Path.GetPathRoot(s) != null)
+			var pathRoot = Path.GetPathRoot(s);
+			if (!string.IsNullOrEmpty(pathRoot))
 			{
-				s = s.Substring(Path.GetPathRoot(s).Length);
+				s = s.Substring(pathRoot.Length);
 			}
 			return s.Replace(Path.DirectorySeparatorChar, '/');
 		}

test/ICSharpCode.SharpZipLib.Tests/Tar/TarTests.cs

@@ -944,7 +944,7 @@ public void rootPathIsRespected()
 			var expectationDirectory = new DirectoryInfo(tempDirectory);
 			foreach (var checkFile in expectationDirectory.GetFiles("", SearchOption.AllDirectories))
 			{
-				var relativePath = expectationDirectory.FullName.Substring(expectationDirectory.FullName.Length);
+				var relativePath = checkFile.FullName.Substring(expectationDirectory.FullName.Length + 1);
 				FileAssert.Exists(Path.Combine(extractDirectory, relativePath));
 				FileAssert.AreEqual(checkFile.FullName, Path.Combine(extractDirectory, relativePath));
 			}
@@ -954,7 +954,7 @@ private void CreateAndClearDirectory(string path)
 		{
 			if (Directory.Exists(path))
 			{
-				Directory.Delete(path);
+				Directory.Delete(path, true);
 			}
 			Directory.CreateDirectory(path);
 		}