> But as an alternative approach for your use case: you could implement a simple wrapper function around `System.get_env` (etc.) that reads/writes to a special key in the process dictionary, falling through to calling the `System` APIs if the process dictionary doesn't have the `:env` key (or whatever you want to call it). > > Then, all you need to do in your tests, is store the env vars you want in the process dictionary of the test, and those will override the global `System` values.
FYI there's a library that does basically exactly this. Maybe it's worth checking out for anyone interested in this approach https://github.com/jbsf2/process-tree -Jason On Fri, Mar 29, 2024 at 6:17 AM Paul Schoenfelder < paulschoenfel...@fastmail.com> wrote: > Ideally, your system pushes this kind of "global" configuration down from > the top of the supervision tree, rather than reading global state like this > in a bunch of places. I would definitely encourage you to try and build > your system with that in mind. Then, all of your tests can pass specific > configuration to the part of the system under test, rather than relying on > global state. > > But as an alternative approach for your use case: you could implement a > simple wrapper function around `System.get_env` (etc.) that reads/writes to > a special key in the process dictionary, falling through to calling the > `System` APIs if the process dictionary doesn't have the `:env` key (or > whatever you want to call it). > > Then, all you need to do in your tests, is store the env vars you want in > the process dictionary of the test, and those will override the global > `System` values. > > Things get a bit trickier when spawning processes is involved, but there > are various approaches for this (I believe ExUnit abuses these pretty > heavily itself IIRC). One of them is to look at the ancestors of the > current process until you either reach the root process, or you find one > with the specified key in the process dictionary. > > The reason why implementing this in ExUnit itself is likely to see > pushback, is because there are just so many ways for this kind of global > state to find its way into a program, and ExUnit cannot handle them all. > Furthermore, I believe José wants to encourage good system design by making > it harder to do things in a not-recommended way, i.e. in this case, not > relying on global configuration deep inside your system. As a practical > matter, it would also require adding the sort of wrapper code I mentioned > to `System.get_env`, which isn't particularly palatable I would imagine. > > Anyway, hope that helps/gives you some ideas! > > Paul > > On Wed, Mar 27, 2024, at 11:14 AM, Daniel Kukula wrote: > > Currently, tests that use env variables can't be run async because the > environment is shared. My proposal is to introduce a with_env function that > will accept a function to execute and a mapping of params that the > functions in System will accept as env variables: > Now: System.put_env("PORT", "4000") > assert some logic > System.delete_env("PORT") > > after > > with_env(%{"PORT" => "4000}, fn -> > assert some logic > end) > > > -- > You received this message because you are subscribed to the Google Groups > "elixir-lang-core" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to elixir-lang-core+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/3e7dcf24-ae69-47b0-a7b5-281055c70726n%40googlegroups.com > <https://groups.google.com/d/msgid/elixir-lang-core/3e7dcf24-ae69-47b0-a7b5-281055c70726n%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- > You received this message because you are subscribed to the Google Groups > "elixir-lang-core" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to elixir-lang-core+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/elixir-lang-core/1392a7b4-dc96-4593-a2f5-3307ff66a5cd%40app.fastmail.com > <https://groups.google.com/d/msgid/elixir-lang-core/1392a7b4-dc96-4593-a2f5-3307ff66a5cd%40app.fastmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. To unsubscribe from this group and stop receiving emails from it, send an email to elixir-lang-core+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/elixir-lang-core/CAHMz6kxrg7qT-4uweiLFXytDAfhErmwLAMKJbSt3xu-aLiHqCg%40mail.gmail.com.
