| name | phx-verify |
| description | Verify Elixir/Phoenix changes — compile, format, and test in one loop. Use after implementation, before PRs, or after fixing bugs. |
Verification Loop
Project-aware verification for Elixir/Phoenix. Reads mix.exs and .check.exs to discover tools, test commands, and custom aliases before running anything.
Iron Laws
- Discover before running — Read
mix.exs first; never run mix credo if credo isn't a dependency
- Prefer ex_check — If
:ex_check + .check.exs exists, mix check replaces individual steps
- Prefer project aliases — If
mix ci or composite alias exists, use it over individual steps
- Run in order — Later steps assume earlier ones pass
- Ask before E2E tests — Unit tests run automatically; E2E/integration tests need user confirmation
- NEVER report success without showing actual command output — "should work" is not verification
Step 0: Project Discovery (ALWAYS FIRST)
Read mix.exs — extract deps/0, aliases/0, and cli/0 (for preferred_envs). Also check for .check.exs. See references/project-discovery.md for full patterns.
Discover tools (deps): :credo, :dialyxir, :sobelow, :ex_check, :excoveralls, :boundary
Discover test commands (aliases + deps):
- Unit:
mix test (always), or custom alias like mix test.with_coverage
- E2E:
mix playwright.test, mix cypress.run, or similar (check preferred_envs for MIX_ENV)
- Fast E2E:
mix playwright.run (skips setup — for re-runs)
Discover composite runner: If .check.exs exists, read it — mix check may handle compile, format, credo, test, dialyzer, sobelow, and more.
Report discovery:
Project tools: compile ✓ | format ✓ | credo ✓ | dialyzer ✓ | sobelow ✓ | ex_check ✓
Test commands: mix test (unit) | mix playwright.test (E2E, MIX_ENV=int_test)
Composite runner: mix check (.check.exs covers: compiler, formatter, credo, dialyzer, sobelow, tests)
Strategy: Running `mix check` then asking about E2E
Verification Sequence
CRITICAL: Before using ANY discovered alias or composite command, verify it works:
- Check the dependency is in
mix.lock (not just mix.exs) — deps may not be fetched
- Run the command — if it fails with "command not found" or dependency error, fall back to individual steps
- Log the fallback: "mix check failed (ex_check not installed?), falling back to individual steps"
If ex_check installed + .check.exs exists: Try mix check. If it fails, fall back to individual steps.
If composite alias found (e.g., mix ci, mix precommit): Try it. If it fails, fall back to individual steps.
Otherwise (or after fallback): Run individual steps, skipping unavailable tools.
Step 1: Compile
mix compile --warnings-as-errors — always
Elixir 1.20+ (OTP 27+): the compiler's built-in type checker emits type
violations / verified bugs as warnings, so --warnings-as-errors now fails
the build on them — no Dialyzer needed. If a previously-green build fails
after a 1.20 bump, suspect a newly-detected type violation, not a regression.
Read the message literally (accepted vs supplied type); it is almost always a
real bug. See ../elixir-idioms/references/elixir-120-type-system.md.
Step 2: Format
mix format --check-formatted — always (auto-fix with mix format if fails)
Step 3: Credo
mix credo --strict — if :credo in deps, else skip
Step 4: Test
mix test --trace — use project test alias if available
Step 5: Dialyzer
mix dialyzer — if :dialyxir in deps, pre-PR only
Step 6: Sobelow
mix sobelow --config — if :sobelow in deps
Skip unavailable tools with: "Credo: ⏭ Not installed"
Step 7: Additional Test Offer
After core verification passes, check if project has additional test commands (E2E, integration, coverage). Ask the user:
Core verification passed. Additional test commands available:
1. mix playwright.test (E2E, MIX_ENV=int_test) — ~5min
2. mix test.with_coverage (unit + coverage report)
Run any of these? [1/2/both/skip]
Respect preferred_envs / cli/0 for correct MIX_ENV on each command.
Quick Reference
| Step | Command | Condition |
|---|
| Discovery | Read mix.exs + .check.exs | Always first |
| Composite | mix check | If :ex_check installed |
| Compile | mix compile --warnings-as-errors | Always |
| Format | mix format --check-formatted | Always |
| Credo | mix credo --strict | :credo in deps |
| Test | mix test --trace | Always (use alias if exists) |
| Dialyzer | mix dialyzer | :dialyxir in deps, pre-PR |
| Sobelow | mix sobelow --config | :sobelow in deps |
| E2E/Extra | Ask user | If additional test commands found |
Usage
- Run
/skill:phx-verify — discovery happens automatically
- Core checks run in order, adapted to project
- After pass, offered additional test commands (E2E, coverage)
- Commit only after all chosen checks pass
