rstest-debugging

Debug Rstest startup, build, runtime, logging, and memory problems systematically. Use when Rstest is slower than Jest/Vitest or a previous baseline; when runner/build/tests/CLI wall disagree; when setup/collect or Node module loading dominates; when mocked modules still enter bundles; when experimental bundle coverage or asset utilization needs inspection; or when dependency bundling, assets, pools, isolation, logs, or memory need evidence-based tuning.