bug#27746: 26.0.50; Need a better test of whether running on Hydra than $NIX_STORE

[Michael Albinus <michael.albinus@gmx.de>]

Gemini Lasswell <gazally@runbox.com> writes:

Hi Gemini,

> There are places in the test code in Emacs which use the existence of
> the NIX_STORE environment variable to change test behavior when
> running on Hydra. However, Emacs should have a different and more
> specific test for whether it is running on Hydra, so that those
> behavior changes don't happen on other machines running NixOS or the
> Nix package manager.

I agree. Checking the existence of $NIX_STORE is just a heuristic. A
better approach might be setting an environment variable or so in the
Emacs recipe for hydra.

Glenn?

> But it would be more generally correct to look at the value of
> NIX_STORE on the machine that REMOTE_TEMPORARY_FILE_DIRECTORY points
> to.

The tests running on hydra use always the mockup file name

(format "/mock::%s" temporary-file-directory)

This is on the local host; a proper test for hydra would be sufficient.

Best regards, Michael.