Fix test suite under Rack 3

[jvendetti]

Problem

The unit test suite passes on develop but fails with 6 errors on master.

Merging develop into master re-resolved Gemfile.lock and bumped rack 2.2.24 → 3.2.7, because the Gemfile declared gem 'rack' with no version constraint:

Branch	rack in Gemfile.lock
develop	2.2.24
master (59b1732e^)	2.2.23
master (before this PR)	3.2.7

Rack 3.0 removed Rack::Server (extracted into the separate rackup gem, which is not in the bundle). test/models/test_ontology_common.rb used it to stand up a throwaway HTTP server serving "test file", which the ontology pull tests download from.

One removed constant, six errors

Test	Mechanism
TestOntologySubmission#test_download_ontology_file	Direct hit — start_server raises NameError: uninitialized constant Rack::Server
TestOntology#test_duplicate_contacts, #test_next_submission_id, #test_ontology_deletes_submissions, #test_ontology_acronym_unique	before_suite starts the same dead server, so nothing listens on the port and goo rejects the save: pullLocation ... does not point to a valid file
TestOntology#test_purl_creation	Collateral. test/test_case.rb sets Thread.abort_on_exception = true, so the dead server thread's NameError is re-raised in the main thread — it landed inside a Net::HTTP call to localhost:9000 (that's GOO_PORT, the triplestore, not purl). enable_purl is false, so this test body never actually ran. It needed no fix of its own.

Changes

Replace Rack::Server with WEBrick::HTTPServer in start_server. webrick is already a test-group dependency, and this works under both rack 2 and rack 3, so it merges back to develop without divergence. Two incidental improvements:

• StartCallback + Queue#pop replaces the old Thread.pass / sleep 3 startup guesswork and blocks until the socket actually accepts. TestOntology.before_suite had no sleep at all — a latent flake.
• thread[:webrick] exposes the server so teardown can shutdown it; Thread.kill alone left the listening socket open until GC.

Pin rack to ~> 3.2 so the major version is a deliberate choice rather than an accident of lockfile re-resolution. The gemspec stays unpinned, as a library's should.

Bump rack-test from ~> 0.6 (0.6.3, released 2014, predates the Rack 3 SPEC) to ~> 2.1. This required adding an explicit require "rack/builder" to the test/rack tests — 0.6.3 loaded all of rack as a side effect, 2.x does not.

Lowercase response header keys in Serializer.response. Rack 3 requires lowercase keys (rack 2's Rack::Utils::HeaderHash used to normalize case and no longer exists). Rack::Utils.set_cookie_header! already emits a lowercase set-cookie, so responses were carrying mixed-case keys and any downstream headers['content-type'] lookup would silently miss.

Rack 3 audit

Checked the rest of the codebase against the installed rack-3.2.7. Rack::Request, Rack::Response#finish, and Rack::Utils.parse_query / build_query / build_nested_query / parse_cookies / set_cookie_header! all still exist and behave correctly. Nothing references the removed Rack::Utils::HeaderHash. Rack::Server was the only removed constant this repo touched.

Testing

Full suite, before and after:

	Before	After
Runs	325	325
Errors	6	0
Failures	0	0
Skips	5	5
Assertions	18012	18025

325 runs, 18025 assertions, 0 failures, 0 errors, 5 skips

Same run count and same 5 skips, so nothing was silently dropped. The 13 added assertions are the test_download_ontology_file assertions that previously never executed because start_server blew up first.

Also verified:

• rake test:rack passes (guards the header-case and rack-test changes).
• test/models/test_ontology.rb run 3× consecutively, 16/16 each time — confirms the startup race is gone.
• No leaked listeners in the 55000–65535 range after the suite, confirming the WEBrick shutdown calls land.
• test_purl_creation passes without being touched, confirming it was collateral rather than a purl problem.

Follow-up, not in this PR

• develop still locks rack 2.2.24 and still has gem 'rack' unpinned, so its next re-resolve can jump to rack 3 on its own and reintroduce this exact breakage there. Everything in this PR works under both rack 2 and 3 except the Gemfile pin — worth pinning develop deliberately to one major version.
• ontologies_api content negotiation. serializer.rb reads env['rack-accept.request'], injected by the rack-accept gem — not a dependency here, unmaintained, no Rack 3 release. This library degrades gracefully (falls back to env["HTTP_ACCEPT"]), but the API app needs checking when it moves to rack 3.

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.03%. Comparing base (fd64046) to head (286ce13).
⚠️ Report is 15 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #318   +/-   ##
=======================================
  Coverage   82.03%   82.03%           
=======================================
  Files         101      101           
  Lines        6853     6853           
=======================================
  Hits         5622     5622           
  Misses       1231     1231           

Flag	Coverage Δ
ag	81.96% <100.00%> (+0.02%)	⬆️
fs	82.00% <100.00%> (+0.07%)	⬆️
gd	81.97% <100.00%> (+0.01%)	⬆️
unittests	82.03% <100.00%> (ø)
vo	81.92% <100.00%> (+0.01%)	⬆️

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