Add Missing Unit Test Coverage for Two Untested StellarService Methods and the Health-Monitor Threshold Logic

[Emmyt24]

Description

backend/src/stellar-service-integration/stellar.service.ts's public getAccountWithSequence and executeTransaction methods have no unit tests in stellar.service.spec.ts (which covers every other public method), and monitoring/health-checks/health-monitor.ts's threshold logic in checkProjectionLag has no test coverage anywhere in the monitoring/ tree despite being straightforward to unit test with a fake query function.

Requirements and Context

• Cover both the success and failure/edge-case paths for each of the three methods
• Use a fake/mock dependency rather than a live network or database call

Suggested Execution

Branch: test/integration-cover-stellar-service-and-health-monitor

Implement Changes

• Add unit tests for getAccountWithSequence and executeTransaction in stellar.service.spec.ts, covering success and failure paths
• Add a new test file for health-monitor.ts's checkProjectionLag, using a fake queryFn to cover both above- and below-threshold cases
• Confirm coverage for all three methods shows up in the existing coverage report

Test and Commit

Run npx vitest run src/stellar-service-integration/__tests__/stellar.service.spec.ts monitoring/health-checks/__tests__ — all three previously-untested code paths have passing unit tests covering success and failure cases.

Example Commit Message

test(integration): add missing unit test coverage for stellar service and health-monitor threshold logic

Closes #<issue>

Guidelines

• Branch from main, open a PR back to main
• All new code must have corresponding tests
• Run npm run lint and npm run test before pushing
• Follow existing naming conventions and file structure
• PR description must reference this issue number (e.g., Closes #<issue>)
• Keep commits atomic and use conventional commit format