Throw ArgumentException when path contains invalid characters (#370)

Fixes #367

Author: robkeim

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

@@ -277,5 +277,20 @@ public void MockFileSystem_AddDirectory_TrailingSlashAllowedButNotRequired(strin
 
             Assert.IsTrue(fileSystem.FileExists(path2));
         }
+
+        [Test]
+        public void MockFileSystem_GetFiles_ThrowsArgumentExceptionForInvalidCharacters()
+        {
+            // Arrange
+            const string path = @"c:\";
+            var fileSystem = new MockFileSystem();
+            fileSystem.AddDirectory(XFS.Path(path));
+            
+            // Act
+            TestDelegate getFilesWithInvalidCharacterInPath = () => fileSystem.Directory.GetFiles($"{path}{'\0'}.txt");
+
+            // Assert
+            Assert.Throws<ArgumentException>(getFilesWithInvalidCharacterInPath);
+        }
     }
 }

System.IO.Abstractions.TestingHelpers/MockDirectory.cs

@@ -97,7 +97,6 @@ public override bool Exists(string path)
 
             try
             {
-
                 path = path.TrimSlashes();
                 path = mockFileDataAccessor.Path.GetFullPath(path);
                 return mockFileDataAccessor.AllDirectories.Any(p => p.Equals(path, StringComparison.OrdinalIgnoreCase));
@@ -176,8 +175,15 @@ public override string[] GetFiles(string path, string searchPattern)
 
         public override string[] GetFiles(string path, string searchPattern, SearchOption searchOption)
         {
-            if(path == null)
-                throw new ArgumentNullException();
+            if (path == null)
+            {
+                throw new ArgumentNullException(nameof(path));
+            }
+            
+            if (path.Any(c => Path.GetInvalidPathChars().Contains(c)))
+            {
+                throw new ArgumentException("Invalid character(s) in path", nameof(path));
+            }
 
             if (!Exists(path))
             {