1. Some incorrect test cases are disabled.
2. Some wrong test cases are corrected.
3. Some new test cases are added.

Change-Id: Ib5d0473d55159f233ddab79f96967eaec7b08597
Reviewed-on: https://go-review.googlesource.com/113736Reviewed-by: Cherry Zhang <cherryyz@google.com>
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>