Added draft implementation of a FileStream-like class. It is not plumbed in at all because I want to discuss the approach first.

Author: Brian McBrayer

src/System.IO.Abstractions/FileStream.cs

@@ -0,0 +1,58 @@
+namespace System.IO.Abstractions
+{
+    /// <summary>
+    /// A <see cref="Stream"/> that has properties similar to <see cref="System.IO.FileStream"/>
+    /// </summary>
+    public class FileStream : Stream
+    {
+        private readonly Stream _wrappedStream;
+
+        /// <summary>
+        /// Constructor for <see cref="FileStream"/>
+        /// </summary>
+        /// <param name="wrappedStream">The underlying wrapped <see cref="Stream"/></param>
+        /// <param name="name">The name of the underlying stream object</param>
+        public FileStream(Stream wrappedStream, string name)
+        {
+            _wrappedStream = wrappedStream;
+
+            Name = name;
+        }
+
+        /// <summary>
+        /// Name of the underlying stream object.
+        /// See <see cref="System.IO.FileStream.Name"/>
+        /// </summary>
+        public string Name { get; }
+
+        /// <inheritdoc />
+        public override bool CanRead => _wrappedStream.CanRead;
+
+        /// <inheritdoc />
+        public override bool CanSeek => _wrappedStream.CanSeek;
+
+        /// <inheritdoc />
+        public override bool CanWrite => _wrappedStream.CanWrite;
+
+        /// <inheritdoc />
+        public override long Length => _wrappedStream.Length;
+
+        /// <inheritdoc />
+        public override long Position { get => _wrappedStream.Position; set => _wrappedStream.Position = value; }
+
+        /// <inheritdoc />
+        public override void Flush() => _wrappedStream.Flush();
+
+        /// <inheritdoc />
+        public override int Read(byte[] buffer, int offset, int count) => _wrappedStream.Read(buffer, offset, count);
+
+        /// <inheritdoc />
+        public override long Seek(long offset, SeekOrigin origin) => _wrappedStream.Seek(offset, origin);
+
+        /// <inheritdoc />
+        public override void SetLength(long value) => _wrappedStream.SetLength(value);
+
+        /// <inheritdoc />
+        public override void Write(byte[] buffer, int offset, int count) => _wrappedStream.Write(buffer, offset, count);
+    }
+}