test(tms): cover the driver-pay domain and service money math

[emoss08]

Description

Third slice of the codebase completeness review: first test coverage for the driver-pay vertical, which previously had zero tests across ~5,000 LOC of money math. Coverage goes from 0% → 61.3% on the driverpay domain package and 0% → 49.8% on driverpayservice (~2,600 lines of tests).

Domain (internal/core/domain/driverpay): escrow account/transaction validation including per-type sign rules (contributions and interest accruals must be positive; applications and refunds negative), funded-percent math and full-funding detection, pay-advance outstanding-balance math and status-sync transitions, pay-code pattern rules, reimbursement classification and the system code catalog, pay-profile component validation, mileage-band validation and rate resolution (including band boundaries and open-ended bands), worker-pay-assignment effective windows and rate overrides, and recurring deduction/earning cap math with next-amount clamping.

Service (internal/core/services/driverpayservice): escrow open (default interest rate from settlement control, duplicate-active-account rejection), adjust (balance-floor enforcement, transaction append with correct BalanceAfterMinor), close (refund of the remaining balance per 49 CFR 376.12(k), no refund on zero balance), interest accrual (exact year-fraction math, accrual-date advancement, ineligible-account no-ops), assignment overlap handling (earlier open assignments get ended at the new effective date; later-starting ones are rejected), rate-override component validation, advance issue/update/write-off transitions, and deduction pay-code direction checks with escrow auto-linking.

The generated mocks don't yet cover the driver-pay repositories (and CLAUDE.md forbids a full mockery regeneration), so the service tests use package-local interface fakes — the same pattern bankreceiptbatchservice's tests use.

Bug found and fixed by the new tests: validateBands rejected contiguous mileage bands (next.MinMiles == previous.MaxMiles) as overlapping, but ResolveMileageRate treats MaxMiles as exclusive — so the only encoding that produces gap-free mileage coverage could not pass validation, silently forcing 1-mile rate gaps in every banded pay profile. The check is now band.MinMiles < prevMax, which still rejects genuine overlaps.

Related Issue or Discussion

Found during a codebase completeness review; maintainer-driven session. Follow-up to #557 and #558.

Type of Change

• Bug fix
• Feature
• Documentation
• Refactor
• Tests
• Build, CI, or infrastructure

Scope

• services/tms/internal/core/domain/driverpay — 6 new test files + the one-line validateBands fix in payprofile.go
• services/tms/internal/core/services/driverpayservice — 4 new test files + shared test fakes

Validation

• Other: go test -cover for both packages (all pass; coverage above), go vet, go build ./internal/..., go test -run TestFullSeedRunOnSQLite ./internal/infrastructure/database/seeder/ (the dev seed still validates after the band fix), gofmt clean, golines applied with the repo's formatter settings. golangci-lint could not run in this environment (binary built with Go 1.25, repo targets Go 1.26).
• cd services/tms && task test — full suite not run in this environment; changed-package tests pass.
• cd services/tms && task lint — see above.
• cd client && pnpm build — not run; no client changes.
• cd client && pnpm lint — not run; no client changes.

Deployment Notes

• The validateBands change only loosens validation (contiguous bands now accepted); every previously-valid pay profile remains valid. No schema, config, or API changes.

Checklist

• I kept the change focused and reviewable.
• I followed AGENTS.md, CLAUDE.md, and existing repository patterns.
• I added or updated tests for behavior changes, or explained why tests are not applicable.
• I updated relevant documentation, examples, migrations, or configuration.
• I did not include secrets, credentials, private customer data, unrelated refactors, or placeholder code.

🤖 Generated with Claude Code

https://claude.ai/code/session_015houJkqb8SuqPW4YpLoWCq

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Generated by Claude Code

[coderabbitai]

✨ Finishing Touches 💡 1

🛠️ Fix failing CI checks 💡

• Create stacked PR
• Commit on current branch

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch claude/driver-pay-tests-b1j99m

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