Verification Loop

Complete verification workflow for Elixir/Phoenix projects. Run this after making changes to ensure code quality before commits or PRs.

Iron Laws

1. Run in order — Later steps assume earlier ones pass; running tests against code with compile warnings produces misleading failures
2. Fix issues immediately — Batching fixes hides which change caused which failure, making debugging harder than the original problem
3. Warnings are errors — Unused variables and deprecated calls accumulate silently until they mask real problems; --warnings-as-errors catches them early
4. Full Dialyzer before PR — Type mismatches caught in review cost 10x more than catching them locally; Dialyzer finds issues tests often miss

Verification Sequence

Execute these commands in order, stopping on any failure:

Step 1: Compilation (Fast Feedback)

mix compile --warnings-as-errors

Catches: Undefined functions, missing modules, type mismatches, unused variables

Step 2: Formatting

mix format --check-formatted

If fails: Run mix format and re-check

Step 3: Credo Analysis

mix credo --strict

Address all issues marked as consistency or design problems

Step 4: Run Tests

# For specific context changes
mix test test/my_app/[changed_context]_test.exs --trace

# For full test suite
mix test --trace

All tests must pass

Step 5: Dialyzer (Pre-PR Required)

mix dialyzer

No new warnings allowed. First run builds PLT cache (slow).

Handling Dialyzer warnings: Prefer fixing over suppressing. If suppression is necessary, add to .dialyzer_ignore.exs with a comment explaining why. Never suppress warnings you don't understand — investigate first.

Quick Reference

Step	Command	Time	When Required
Compile	mix compile --warnings-as-errors	Fast	Always
Format	mix format --check-formatted	Fast	Always
Credo	mix credo --strict	Medium	Always
Test	mix test --trace	Medium	Always
Dialyzer	mix dialyzer	Slow	Before PR

Usage

After making code changes:

1. Run /phx:verify to execute the full loop
2. Address any failures before proceeding
3. Commit only after all checks pass

For partial verification during development, run individual steps as needed.