Files
claude-foundations/best-practices/validation.md
Paul O'Reilly 1b5e73dc54 Distill best practices from agent-runtimes M1-M3 memory files
12 additions/updates across 5 best-practice files:
- docker-uid-matching: userdel simplification, SSH agent socket UID match
- debugging: GIT_SSH_COMMAND scope limitation
- test-driven-development: subprocess mock gotcha, routing callables,
  Pydantic v2 field_validator defaults, sys.exit at module level
- spec-driven-development: multi-agent orchestration practices (commit WIP,
  self-verify, import conventions, assembly budget)
- validation: test pre-commit hooks after adding dependencies

Source: agent-runtimes/memory/ (decisions, gotchas-docker, gotchas-python,
process-lessons, m1/m2/m3 reflections)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
2026-03-25 11:11:54 +13:00

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3.6 KiB
Markdown

# Validation & Deployment
## Validate Locally, Deploy Once
The single biggest time sink across projects is "deploy first, validate later." Real-world stats from a 9-milestone infrastructure project showed 50-60% of commits were fixes that could have been caught locally.
**Always validate before pushing:**
- `helm template` for Helm chart values
- `kustomize build` (or `kubectl kustomize`) for Kustomize apps
- `kubectl apply --dry-run=server` for K8s naming/schema issues
- `docker run <app> validate-configuration` for apps that support it (Authelia, Homepage, etc.)
- `docker inspect` for unfamiliar container images before writing init containers
- Lint/typecheck/test for application code
**Batch fixes locally, push once.** Each push-sync-crash-fix cycle wastes minutes and clutters Git history.
## Test the Full Chain Immediately
After wiring up any new service or endpoint, test end-to-end from the user's perspective right away. Don't assume intermediate steps working means the whole chain works.
- `curl --resolve domain:443:<ip> https://domain` to test bypassing DNS/proxy layers
- Test from the actual consumer (not same-namespace test pods for network policies)
- Test DNS resolution after deploying FQDN-based policies
## Pre-Flight Checks
Before starting a deploy or automation phase:
- Verify SSH keys are loaded (`ssh -T git@<host>`)
- Confirm environment variables and credentials are available
- Check that the target environment is in the expected state
- Verify DNS records resolve as expected
## Scripts That Change Config Must Self-Verify
After updating and restarting a service, the script should test that the change actually took effect (e.g., curl an API endpoint, check a config value). A "success" message without verification hides failures.
## Check Container Image Runtime Requirements First
Before writing deployment manifests (StatefulSets, Deployments, init containers), check the image's runtime expectations: UID it runs as, writable directories it needs, filesystem layout. Use `docker inspect` or image documentation.
Modern images often run as non-root with specific writable directory requirements that aren't obvious from docs alone. Discovering these at deploy time wastes an entire push-crash-fix cycle per missed requirement.
## Verify Counts and Summaries Mechanically
After editing specification or documentation files that include summary counts (e.g., "14 requirements"), verify them with `grep` or `wc` rather than counting manually. Manual counting of dozens of items is error-prone and produces incorrect summaries that erode trust in the documentation.
## Test Pre-Commit Hooks Manually After Adding Dependencies
Run `bash .githooks/pre-commit` (or your hook path) manually after adding new dependencies or changing test imports. Hidden virtual environments (`.venv/`) that the hook discovers before system Python can cause `ModuleNotFoundError` at commit time even though tests pass from the terminal. Discovering hook failures during a real commit wastes debugging effort on environment issues rather than code issues. After adding a dependency, check all Python environments: `find . -name "activate" -o -name "pytest"` to discover venvs, and install into each.
## Order Multi-Step Migrations Carefully
When performing multi-step changes on remote systems (port changes, firewall rules, service migrations), plan explicit ordering to avoid lockout:
1. Open the new path first (new port, new firewall rule)
2. Migrate the service to use the new path
3. Add redirects or backward-compatibility rules
4. Remove the old path
Doing all steps at once risks losing access if any step fails. Plan the ordering upfront, not mid-deploy.