Verification Loop

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

Iron Laws

• Run in order — Later steps assume earlier ones pass; running tests against code with compile warnings produces misleading failures

• Fix issues immediately — Batching fixes hides which change caused which failure, making debugging harder than the original problem

• Warnings are errors — Unused variables and deprecated calls accumulate silently until they mask real problems; --warnings-as-errors catches them early

• 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:

• Run /phx:verify to execute the full loop

• Address any failures before proceeding

• Commit only after all checks pass

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