Add FinOps xunit tests -- scenario-based recommendation validation (#564)

[erikdarlingdata]

Summary

• Add 16 xunit tests for the FinOps recommendation engine and High Impact scorer
• Fix BigInteger handling bug in maintenance and storage tier FinOps checks (DuckDB SUM() returns HUGEINT -> BigInteger, which Convert.ToInt64/32 cannot handle)
• Tests cover: over-provisioned enterprise, idle databases, high impact query skew, HighImpactScorer pure function, long-running jobs, clean server, reserved capacity, bursty CPU, VM right-sizing, and low IO latency scenarios

Test plan

• All 16 FinOps tests pass (dotnet test --filter FinOpsTests)
• BigInteger bug fix verified: maintenance and storage tier recommendations now fire correctly
• Clean server scenario confirms no false positives from DuckDB-based checks

🤖 Generated with Claude Code

Summary by CodeRabbit

• Tests
  • Added comprehensive test coverage for FinOps recommendations and scoring functionality, validating resource optimization scenarios including CPU/memory right-sizing, idle database detection, query performance impact analysis, and reserved capacity behavior.

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

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Review profile: CHILL

Plan: Pro

Run ID: bb3f59db-c78b-48b4-934e-37049c7c745b

📥 Commits

Reviewing files that changed from the base of the PR and between 1b3a47f and f1c2cb4.

📒 Files selected for processing (2)

• Lite.Tests/FinOpsTests.cs
• Lite/Services/LocalDataService.FinOps.cs

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📝 Walkthrough

Walkthrough

Adds a comprehensive end-to-end test suite for FinOps scenarios covering over-provisioned infrastructure, idle databases, high-impact queries, and reserved capacity analysis. Also updates type conversion helpers in LocalDataService.FinOps when reading numeric values from data readers.

Changes

Cohort / File(s)	Summary
FinOps Test Suite Lite.Tests/FinOpsTests.cs	Introduces 16 test methods covering enterprise VM right-sizing, idle database detection, cost-share calculations, dominant query scoring, long-running job recommendations, clean server filtering, CPU reserved capacity analysis, and storage tier recommendations. Tests leverage in-memory DuckDB, TestDataSeeder, and LocalDataService for end-to-end validation.
LocalDataService Type Conversions Lite/Services/LocalDataService.FinOps.cs	Replaces 8 occurrences of Convert.ToInt64(...) with a ToInt64(...) helper method when reading numeric job metrics (avgDuration, maxDuration, avgHistorical, timesLong) and server IO metrics (totalReads, totalStallRead, totalWrites, totalStallWrite).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~25 minutes

Possibly related PRs

• No additional related PRs identified beyond those already referenced in the changeset summary.

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch feature/finops-xunit-tests

📝 Coding Plan

• Generate coding plan for human review comments

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