tree c750555cf58bdec68ac87f8a9faf0d84559c71c0
parent cfb5802a8016b79bdcceee950492780b4193550a
author Nan Zhou <nanzhoumails@gmail.com> 1640718176 -0800
committer Nan Zhou <nanzhoumails@gmail.com> 1641319066 -0800

Use nested namespace

Nested namespace is introduced in C++ 17. This saves nearly 50 lines.
This change also puts tests into a nested namespace, which saves
unnecessary using directives.

Signed-off-by: Nan Zhou <nanzhoumails@gmail.com>
Change-Id: I7c3e38588fd5c2cbd83ac13ee24327318e8c06a4