ci: refactor julia/r/conda tests - now ~25 min instead of ~50 min

[consideRatio]

Previously the CI system took ~50 minutes. The tests in the folders tests/conda, tests/julia, and tests/r all took longer than 25 minutes but are now reduced to about ~25 minutes or less.

Change description

• Deleted and merged tests Test coverage is retained well I think, even expanded towards modern versions. Overall the following principles guided what I retained.
  • oldest - py2, py3.5, r3.6?, julia 1.0.2? (Project.toml buildpack), julia 0.6.4? (REQUIRE buildpack) See #1192
  • default - py3.7, r4.2, julia latest (Project.toml buildpack), julia 0.6.4 (REQUIRE buildpack) See #1190
  • latest - py3.10, r4.2, julia latest (Project.toml buildpack)
  • before and after - R with mran and R with rspm, julia environment variables after 1.0+
  • pinnability - ensure language versions can be pinned
  • functionality - binder folder, description file, requirements file, etc.
• Renamed test folders, added/updated READMEs

Test changes

Changes to tests/conda

After	Before	Note
py35-binder-dir	binder-dir py37	Makes an old version the oldest version, and merges in the binder directory test
py310-requirements-file	py38 requirements	Makes a less old version the latest version, and merges in the requirements file test
py2	simple-py2	Renamed
r-postbuild	r-unspecified default-env simple r4.0 r4.1	Merges in the postBuild file test (default-env), merges tests of modern R versions into the latest version (r4.0, r4.1), merges tests of the default Python version (simple)
r3.6-extra-args	repo-path r3.6	Merges extra-args.yml file test with r3.6 pinning test
-	channel-dep	A deleted test, testing functionality part of mamba since 0.6 introduced more than two years ago

Changes to tests/r

After	Before	Note
r3.6-mran	r3.6	Renamed
r4.0-mran	mran, r4.0	Merges similar tests
r4.0-rspm	r4.0-rspm, r4.1	Merges r4.0 and r4.1,
r-rspm-apt	apt, simple	Merges in the apt.txt file test
r-rspm-description	description-file	Renamed

Changes to tests/julia

After	Before	Note
project	julia_version-default	Merges in the requirements file test
project-1.0.2	julia_version-1.0.2	Renamed
require	julialegacy_version-0.6.3	The default version for require is 0.6.4, and can be used to test the oldest version.
require-1-requirements	pyplot-requirements julialegacy_version-1 julialegacy_version-1.0 julialegacy_version-1.1	Merged similar tests

Before

After

[manics]

To help with review would you mind explaining the overall thoughts behind your changes? For example, what's your thinking behind bumping versions instead of leaving them as they are?

I think we should keep intermediate versions, for example an old bug was included installing the wrong version of R when 4.0 was requested https://github.com/jupyterhub/repo2docker/issues/1077 so this should be kept as a regression test.

[consideRatio]

@manics I've updated the PR description with a declaration of the principles that has guided me when refactoring this! I think we still cover #1077 in the R buildback by testing both before (mran) and after (rspm) situations.

[consideRatio]

Sorry for the noise in this PR @manics @yuvipanda, with a lot of force pushes and too early transition from a draft PR to a ready for review PR.

At this point, it is ready for review though!

[manics]

Thanks for the additional description- it makes sense, though I'm still struggling to review the actual changes. I'm also concerned we're going to loose some of the information on the purposes of individual tests, which is a problem for any future refactoring.

I noticed you added a few READMEs in some tests, what do you think about adding READMEs for each group of tests instead/as well, e.g.

tests/conda/README.md
tests/julia/README.md
tests/r/README.md

where each file describes how the subtests in that directory combines multiple factors, such that they cover all combinations?

[consideRatio]

I'm still struggling to review the actual changes.

I'm sorry about this, if you have a suggestion on what I can do to help let me know. I have considered breaking apart this refactoring PR into pieces such as one for the conda buildpacks tests, and one for julia, and one for R. Doing that though would make common aspects need to be discussed in separate PRs, such as the README suggestion etc and I figure it wouldn't be very helpful.

I'm also concerned we're going to loose some of the information on the purposes of individual tests, which is a problem for any future refactoring.

Having worked with these files many hours now, I'm quite confident this is an improvement with regards to future refactoring work. The git history will be obfuscated by this refactor, but the documentation surrounding the tests will be accurate and updated. I've been surprised several times by un

I noticed you added a few READMEs in some tests, what do you think about adding READMEs for each group of tests instead/as well, e.g.

tests/conda/README.md
tests/julia/README.md
tests/r/README.md

where each file describes how the subtests in that directory combines multiple factors, such that they cover all combinations?

:100: implemented now!

[yuvipanda]

LET'S GOOOOO! THANK YOU SO MUCH @MANICS AND @CONSIDERATIO!

[yuvipanda]

let it be known that I tried to upper case your usernames too ^ but github autocorrected them