Add end-to-end tests for IntermediateStateCalcStageV2 availability-aware prioritization

[ngngwr]

Issues

• My PR addresses the following Helix issues and references them in the PR description:

Follow-up to #131 — adds end-to-end test coverage for the V2 pipeline and availability-aware ordering code path.

Description

• Here are some details about my PR, including screenshots of any UI changes:

PR #131 added the V2 config flag and delegation logic but had zero end-to-end tests for the availability-aware code path (IntermediateStateCalcStageV2.java:118-120). This PR closes that gap with two new test classes:

TestIntermediateStateCalcStageV2 — Subclass that runs all 8 V1 IntermediateStateCalcStage tests with V2 enabled via setIntermediateStateCalcStageV2Enabled(true), verifying backward compatibility of the V2 pipeline.

TestIntermediateStateCalcStageV2AvailabilityAware — Extends V2 tests with availability-aware prioritization enabled. Inherits 9 V1/V2 tests plus adds 3 new scenarios that verify availability-aware-specific ordering behavior under tight throttle budgets:

• Recovery prioritization: fully-degraded resources (top state missing, score 1M) win recovery slots over partially-degraded ones
• Handoff prioritization: top-state handoff transitions (score 999K) win over normal upward transitions
• Load-balance gradient ordering: the upward score formula minActive/(currentActive+1) correctly prioritizes more-degraded resources for load-balance messages

Tests

• The following tests are written for this issue:

• TestIntermediateStateCalcStageV2 — 9 tests (8 inherited V1 + 1 routing guard)

• TestIntermediateStateCalcStageV2AvailabilityAware#testAvailabilityAwarePrioritizesMostDegradedResource

• TestIntermediateStateCalcStageV2AvailabilityAware#testAvailabilityAwareHandoffPrioritizedOverUpwardTransition

• TestIntermediateStateCalcStageV2AvailabilityAware#testAvailabilityAwareOrdersByDegradationForLoadBalance

• The following is the result of the "mvn test" command on the appropriate module:

mvn test -pl helix-core -Dtest="TestIntermediateStateCalcStage,TestIntermediateStateCalcStageV2,TestIntermediateStateCalcStageV2AvailabilityAware"

Tests run: 31, Failures: 0, Errors: 0, Skipped: 0
BUILD SUCCESS

Changes that Break Backward Compatibility (Optional)

None. This PR adds test files only — no production code changes.

Commits

• My commits all reference appropriate Apache Helix GitHub issues in their subject lines.