Move conformance tests into AA itself (possibly in a package extension)

[fingolfin]

Right now, in order to run ring conformance tests in the REPL (e.g. to debug issues with them), one has to do something like this:

import AbstractAlgebra, Test
include(joinpath(pathof(AbstractAlgebra), "..", "..", "test", "Rings-conformance-tests.jl"))

before invoking e.g. test_Field_interface_recursive.

In many cases this then runs into an error because actually you also need to find and run one or more test_elem methods which are used by the conformance tests for the particular ring you are interested in.

All of this could be solved if we integrated Rings-conformance-tests.jl directly into AbstractAlgebra, so that its tests are available after using AbstractAlgebra.

This would require adding Test as a dependency. Doesn't seem like a major issue to me, but even that could be avoided by putting the code into a package extension (which would imply upping the minimal required Julia version to at least 1.9, IIRC).

Then packages like Nemo could do the same, and implement test_elem methods directly in the package (while we are at it, we could also rename test_elem, it was a bit of a spur of the moment decision to use that name -- as usual, naming things well is one of the hardest problems...)

Afterwards, you could just do

using Nemo, Test
test_Field_interface_recursive(GF(5))

or whatever, and it would "just work".

(This is idea is not new, and at the very least @lgoettgens also came up with essentially the same idea. But I realized now that we don't have an issue.)

[fingolfin]

Of course this is about all conformance tests: for rings, fields, matrix spaces, but also e.g. groups, and stuff we don't have yet.

[lgoettgens]

I am happy to look into doing this. I would try to first do this in a backwards-compatible way, i.e. that this still works using the current include in all julia versions back to 1.6 (so that we can update our downstream packages in a non-breaking way).

[thofma]

I would prefer if we could make Test not a dependency. (Apart from that, I like the idea.)

[fingolfin]

We could follow the Julia docs and use Requires.jl for Julia 1.6-1.8, and package extensions above.

@lgoettgens that kind of backwards compatibility would indeed be useful. Presumably this would mean test/Rings-conformance-tests.jl in AA stays but is changed to something like this:

using AbstractAlgebra.ConformanceTests

and export statements in there would make available test_elem, test_Ring_interface etc.