Build error-budget gate tests - SLO + error-budget calculation per Google SRE workbook ("difference between target uptime and actual uptime"); burn-rate alerting; monthly-budget exhaustion test; freeze-trigger when budget consumed. Per sre.google embracing-risk reference. Includes the incident-metrics reference for MTTR / MTBF / MTTD / MTTA - per-incident record schema, calculation formulae, exclusion rules, dashboards-as-code, and target-vs-actual alerting. Use when an SLO and error budget are written down but nothing verifies that burn-rate alerts fire or that the release freeze engages when the budget runs out, or when MTTR / MTBF dashboards report numbers nobody can reproduce.