This extracts some of the test code from packages, and adds the ability to run
the same test with multiple drivers.
This should generally be useful for all tools that run on top of go/packages as
well when writing tests for them.
Change-Id: I88c596ad07c0782270c5798d92ae29f7549943cf
Reviewed-on: https://go-review.googlesource.com/c/140118
Run-TryBot: Ian Cottrell <iancottrell@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Michael Matloob <matloob@golang.org>
Ian Cottrell