Migrate xUnit v2 tests to xUnit v3 on Microsoft Testing Platform

[Mikael Weaver (mikaelweave)]

Description

Migrate the test suite from xUnit v2 to xUnit v3 while continuing to use Microsoft Testing Platform.

• Keep the existing datastore and format test variants.
• Keep the existing CI test partitions and retry behavior.
• Replace v2 test filters with equivalent xUnit v3 filters.
• Remove obsolete custom retry and runner code.
• Keep only the custom fixture support required by this repository.

This change does not alter FHIR product behavior or the SQL schema.

Related issues

Addresses AB#189958.

Testing

• The PR pipeline passed in build 51284.
• R4 and R5 SQL E2E result sets matched the migration baseline with no missing or added tests across 2,136 R4 and 1,922 R5 results.
• R4 Integration discovery matched main with no missing tests for the full, SQL, and Cosmos selections.
• CodeQL passed.

FHIR Team Checklist

• Update the title of the PR to be succinct and less than 65 characters
• Add a milestone to the PR for the sprint that it is merged (i.e. add S47)
• Tag the PR with the type of update: Bug, Build, Dependencies, Enhancement, New-Feature or Documentation
• Tag the PR with Open source, Azure API for FHIR (CosmosDB or common code) or Azure Healthcare APIs (SQL or common code) to specify where this change is intended to be released.
• Tag the PR with Schema Version backward compatible or Schema Version backward incompatible or Schema Version unchanged if this adds or updates Sql script which is/is not backward compatible with the code.
• When changing or adding behavior, if your code modifies the system design or changes design assumptions, please create and include an ADR.
• CI is green before merge
• Review squash-merge requirements

Semver Change (docs)

Skip

[Codecov Comments Bot (codecov-commenter)]

Codecov Report

✅ All modified and coverable lines are covered by tests.
⚠️ Please upload report for BASE (main@da355bc). Learn more about missing BASE report.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5762   +/-   ##
=======================================
  Coverage        ?   78.64%           
=======================================
  Files           ?     1017           
  Lines           ?    36981           
  Branches        ?     5638           
=======================================
  Hits            ?    29085           
  Misses          ?     6479           
  Partials        ?     1417           

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• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.
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[Mikael Weaver (mikaelweave)]

Status: full pipeline is green — one owner action left

ADO build 51080 completed succeeded: 42 / 42 jobs, 22 / 22 stages, 0 failed, 0 skipped.
GitHub checks: 47 pass / 0 fail / 1 pending.

Every stage this change actually touches has now executed for real — all five E2E legs on both data
stores across R4 / R5 / STU3, all five reindex legs, all three bulk-update legs, and all five
integration legs. Their executed counts match two independent v2 control builds test-for-test and
skip-for-skip; see the new “Live CI evidence” section in the PR description for the 18-leg
table, including the three legs that differ and why the controls prove the migration is not the cause.

---

The one thing I cannot do for you: Check Metadata

This is the only non-passing check, and it is not a test or build failure. The workflow requires a
DevOps work item reference in the PR description:

if (body.toLowerCase().includes('ab#') == false && ...)
  errors += '- FHIR Team: A DevOps workitem is required. Use AB#123 syntax or link to DevOps item.'

Action: add AB#<id> to the PR description with the real work item number. I deliberately did not
invent one — a fabricated ID would link this PR to the wrong work item, and that is worse than a red
check. This is a one-line edit and the check goes green.

(Note: the run against this head recorded startup_failure, so the check currently reads pending
rather than fail. Re-running it after the AB# is added will resolve both.)

---

Why this PR replaced #5761

#5761 was raised from a fork. On this repository a cross-fork PR does not get the secrets needed by
Setup Test Environment, that stage failed, and it cascaded downstream. Both PRs run the same
22-stage pipeline — but on the fork build (51075)
only 7 stages ran, 1 failed and 14 were skipped, so not one test leg ever executed
(26 GitHub checks, 7 of them failing). On this PR, all 22 stages ran and all 22 succeeded (48 checks,
0 failing). Since the entire question this change raises is "do the test legs still select and run the
same tests?", #5761 could not be evaluated on its merits.

This PR runs from a branch on microsoft/fhir-server itself, which is why the matrix above exists.
#5761 is closed and superseded; the head commit is identical apart from the retry-residue cleanup
(d3e65a87b).

---

Suggested reading order for reviewers

The description is long because the claims are quantified, but it is structured for skimming — every
section past the summary is collapsed. If you only read three things:

1. “Live CI evidence” — the 18-leg table above. This is the primary gate.
2. “Net growth ≠ review surface” — which files actually need human eyes (six, not 144).
3. “Integration-leg exclusion filters — a regression found late, and fixed” — the one place the
   mechanical port went wrong, how it was caught, and the proof it is fixed.

Net change is −509 lines across 144 files: this migration deletes custom test infrastructure
rather than adding to it.