Add comprehensive testing improvement plan

[dillonvargo]

Description of what I changed

Added a markdown planning document (testing-improvement-plan.md) at the repository root that outlines a prioritized strategy for improving test coverage across OpenMRS Core. The document covers four areas:

1. P1 - Missing assertion validation: Proposes a new meta-test in OpenmrsTestsTest.java to detect test methods that lack assert*/verify* calls (addresses the existing TODO at lines 39-42).
2. P2 - Disabled test remediation: Inventories all 40+ @Disabled tests across 21 files, categorized into three tiers (ticket-referenced, no-ticket, and intentionally-disabled utilities), with action items for each.
3. P3 - AOP void method coverage: Analyzes the BaseVoidHandler/RequiredDataAdvice AOP pattern that causes low branch coverage in void* service methods (TRUNK-5151), and proposes testing strategies.
4. P4 - JaCoCo infrastructure: Proposes adding report and check goals to the existing JaCoCo config to enforce coverage thresholds.

No code changes — this is a planning document only.

Issue I worked on

This plan references multiple existing tickets:

• see https://issues.openmrs.org/browse/TRUNK-5151
• see https://issues.openmrs.org/browse/TRUNK-1956
• see https://issues.openmrs.org/browse/TRUNK-4772
• see https://issues.openmrs.org/browse/TRUNK-3945
• see https://issues.openmrs.org/browse/TRUNK-4212
• see https://issues.openmrs.org/browse/TRUNK-4704
• see https://issues.openmrs.org/browse/TRUNK-5153
• see https://issues.openmrs.org/browse/TRUNK-6083

Checklist: I completed these to help reviewers :)

• My IDE is configured to follow the code style of this project.
• I have added tests to cover my changes. (If you refactored existing code that was well tested you do not have to add tests)
  • N/A — no code changes, documentation only.
• I ran mvn clean package right before creating this pull request and added all formatting changes to my commit.
• All new and existing tests passed.
• My pull request is based on the latest changes of the master branch.

Items for reviewer attention

• Should this document live in the repo root? Consider whether a wiki page or JIRA epic would be a more appropriate home. If kept in-repo, it may warrant a docs/ directory.
• Verify the disabled test inventory is complete — the count of 40+ @Disabled annotations across 21 files was gathered via grep; confirm nothing was missed or miscounted.
• Evaluate proposed assertion validation approach — the plan suggests ASM bytecode analysis to detect assertion-less tests. Confirm this aligns with the project's preferences (vs. simpler source-file scanning).
• Review timeline estimates — 20-30 engineering days total is a rough estimate without team capacity context.

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Link to Devin run: https://app.devin.ai/sessions/f85e30cdef124cceb11ddef199f6d780
Requested by: Dillon Vargo (dillon.vargo@windsurf.com)

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