- clearGuestMetadataCache: nil safety, cache clearing, key isolation - shouldRunBackupPoll: interval-based, cycle-based, config validation - storeNodeLastSuccess/lastNodeSuccessFor: store/retrieve, overwrite, missing keys Improves coverage for backup polling logic and node metrics tracking.
Test normalizeLabel, normalizeNodeLabel, splitInstanceKey, breakerStateToValue, sanitizeInstanceLabels, makeMetricKey, and makeNodeMetricKey with 36 test cases covering edge cases like empty strings, whitespace, and invalid inputs.
