cabal test should set GHC_PACKAGE_PATH

I have a package that dynamically loads another package at runtime via hint.

When I build it with a cabal sandbox, the test suite fails to find the other package if run with "cabal test", but works fine when run with "cabal exec".

I guess that "cabal test" should be setting GHC_PACKAGE_PATH like cabal exec does?

I get this with cabal 1.20 and 1.22.

Start by reproducing the sandbox behavior with "cabal test" and compare it with "cabal exec" using a package that dynamically loads another package via hint. Trace where GHC_PACKAGE_PATH is established for each command. Done means the test suite can find the dynamically loaded package when run with "cabal test" in a Cabal sandbox.

Written by the indexing model from the issue text.