Elixir Verification Gate: Evidence or It Didn't Happen

THE IRON LAW

NEVER claim something works without running it and reading the output.

Not "should work". Not "looks correct". Not "I think it passes".

RUN IT. READ IT. PROVE IT.

ABSOLUTE REQUIREMENT

Before claiming ANY of the following, you MUST provide evidence:

1. "Tests pass"

MUST run: mix test MUST read: Actual test output showing "X tests, 0 failures" MUST provide: Exact output or test count

# Required evidence
$ mix test
..........

Finished in 0.3 seconds (0.1s async, 0.2s sync)
10 tests, 0 failures

# This is evidence ✓

2. "Code compiles"

MUST run: mix compile --warnings-as-errors MUST read: Output showing "Compiled" or error messages MUST provide: Confirmation of zero warnings

# Required evidence
$ mix compile --warnings-as-errors
Compiling 5 files (.ex)
Generated my_app app

# This is evidence ✓

3. "Code is formatted"

MUST run: mix format --check-formatted MUST read: Output or lack thereof MUST provide: Confirmation no files would be formatted

# Required evidence
$ mix format --check-formatted
# (no output means all files formatted)

# This is evidence ✓

4. "Credo passes"

MUST run: mix credo --strict MUST read: Analysis results MUST provide: Confirmation of "no issues found"

# Required evidence
$ mix credo --strict
Checking 42 source files...

Please report incorrect results: https://github.com/rrrene/credo/issues

Analysis took 0.3 seconds (0.2s to load, 0.1s running 100 checks on 42 files)
17 mods/funs, found no issues.

# This is evidence ✓

5. "Dialyzer passes"

MUST run: mix dialyzer MUST read: Type checking results MUST provide: "done (passed successfully)" message

# Required evidence
$ mix dialyzer
...
Total errors: 0, Skipped: 0, Unnecessary Skips: 0
done (passed successfully)

# This is evidence ✓

6. "Migration runs successfully"

MUST run: mix ecto.migrate MUST read: Migration execution output MUST provide: Confirmation migration completed

# Required evidence
$ mix ecto.migrate

15:42:13.456 [info] == Running 20231201150000 MyApp.Repo.Migrations.CreateUsers.change/0 forward

15:42:13.458 [info] create table users

15:42:13.478 [info] == Migrated 20231201150000 in 0.0s

# This is evidence ✓

7. "Function works correctly"

MUST run: Test that exercises the function MUST read: Test output showing it passes MUST provide: Example usage or test code

# Required evidence
test "create_user/1 with valid attrs creates user" do
  attrs = %{name: "Alice", email: "alice@example.com"}
  assert {:ok, %User{} = user} = Accounts.create_user(attrs)
  assert user.name == "Alice"
  assert user.email == "alice@example.com"
end

# ✓ Test passes with actual run

8. "Issue is fixed"

MUST run: The command that revealed the issue MUST read: Output showing issue no longer appears MUST provide: Before/after comparison

# Required evidence - BEFORE
$ mix dialyzer
lib/my_app.ex:42:pattern_can_never_match
Total errors: 1

# Applied fix...

# Required evidence - AFTER
$ mix dialyzer
Total errors: 0, Skipped: 0, Unnecessary Skips: 0
done (passed successfully)

# This is evidence ✓

BANNED PHRASES (Without Evidence)

These phrases are BANNED unless accompanied by actual command output:

❌ "The tests should pass" ❌ "This should compile" ❌ "I believe this works" ❌ "This looks correct" ❌ "The code appears to be working" ❌ "I think this fixes it" ❌ "This ought to work" ❌ "Assuming the tests pass" ❌ "If you run the tests, they'll pass" ❌ "The build will succeed"

Instead, RUN THE COMMAND and report actual results.

VERIFICATION CHECKLIST

Before claiming you're done with ANY task:

• I ran the relevant commands (not just wrote code)
• I read the actual output (not assumed it worked)
• I saw success messages with my own eyes
• I can quote the exact output
• All tests actually pass (I ran them)
• Code actually compiles (I compiled it)
• No warnings exist (I checked)
• Quality checks actually pass (I ran them)

If you can't check ALL boxes with evidence, you're not done.

EXAMPLES OF PROPER VERIFICATION

Example 1: Claiming Tests Pass

WRONG:

I've implemented the create_user function. The tests should pass now.

RIGHT:

I've implemented the create_user function. Running tests:

$ mix test test/my_app/accounts_test.exs
..........

Finished in 0.2 seconds (0.1s async, 0.1s sync)
10 tests, 0 failures

✓ All tests pass.

Example 2: Claiming Code Compiles

WRONG:

I've fixed the compilation error. It should compile now.

RIGHT:

I've fixed the compilation error. Compiling:

$ mix compile --warnings-as-errors
Compiling 1 file (.ex)
Generated my_app app

✓ Compiles with zero warnings.

Example 3: Claiming Dialyzer Is Happy

WRONG:

I added the @spec. Dialyzer won't complain anymore.

RIGHT:

I added the @spec. Running Dialyzer:

$ mix dialyzer
Finding suitable PLTs
Checking PLT...
...
Total errors: 0, Skipped: 0, Unnecessary Skips: 0
done (passed successfully)

✓ Dialyzer passes with zero errors.

Example 4: Claiming Migration Works

WRONG:

The migration is ready and should run fine.

RIGHT:

Running the migration:

$ mix ecto.migrate

15:42:13.456 [info] == Running 20231201150000 MyApp.Repo.Migrations.CreateUsers.change/0 forward
15:42:13.458 [info] create table users
15:42:13.478 [info] == Migrated 20231201150000 in 0.0s

✓ Migration executed successfully.

WHEN VERIFICATION FAILS

If you run a command and it fails:

DO NOT:

• Claim it works anyway
• Say "it should work, not sure why it's failing"
• Move on to other tasks
• Assume the failure is environmental

INSTEAD:

1. Read the error message completely
2. Understand what failed and why
3. Fix the actual problem
4. Run the command again
5. Verify it now passes
6. Provide evidence of success

VERIFICATION WORKFLOW

For EVERY change you make:

1. Make the change

# Edit code
def create_user(attrs) do
  # ... implementation
end

2. Run the relevant test

$ mix test test/my_app/accounts_test.exs:42
.

Finished in 0.1 seconds
1 test, 0 failures

3. Run full test suite

$ mix test
..........

Finished in 0.3 seconds
10 tests, 0 failures

4. Run quality checks

$ mix format --check-formatted
$ mix credo --strict
$ mix dialyzer

5. Report results

✓ Tests pass (10/10)
✓ Code formatted
✓ Credo: no issues
✓ Dialyzer: 0 errors

Only THEN can you claim the task is complete.

INTEGRATION WITH OTHER SKILLS

This skill works with:

• elixir-tdd-enforcement - Verify tests fail (RED), verify tests pass (GREEN)
• elixir-no-shortcuts - Verify error is gone (not suppressed)
• elixir-root-cause-only - Verify root cause is fixed (not symptom)

Example TDD verification:

1. Write test → RUN → See it fail ← VERIFICATION
2. Implement → RUN → See it pass ← VERIFICATION
3. Refactor → RUN → See it still passes ← VERIFICATION

SPECIAL CASES

"I can't run tests because..."

STOP. Fix the environment so you CAN run tests. Testing is non-negotiable.

"The tests are flaky"

STOP. Fix the flakiness before proceeding. Flaky tests = broken tests.

"Dialyzer takes too long"

Run it anyway. Cache the PLT. Use mix dialyzer --incremental. No shortcuts.

"I'm just writing documentation"

Still verify. Run mix docs and confirm it generates without warnings.

"It's just a comment change"

Still verify. Run mix format --check-formatted and ensure formatting is maintained.

RATIONALIZATIONS THAT ARE WRONG

"I don't need to run it, the code is obviously correct"

WRONG. Code is never obviously correct. Computers are precise. Run it.

"I ran it locally yesterday, still works"

WRONG. Run it NOW, in THIS context, with THESE changes.

"The CI will catch it"

WRONG. Catch it locally BEFORE pushing. CI is last resort, not primary check.

"I'm confident this works"

WRONG. Confidence without evidence is just hope. RUN. THE. COMMAND.

"Trust me, I know what I'm doing"

WRONG. Trust, but verify. Actually, just verify. Evidence > trust.

CONSEQUENCES OF SKIPPING VERIFICATION

If you claim something works without running it:

1. It probably doesn't work - Murphy's Law applies
2. You waste everyone's time - Including your own
3. Bugs reach production - Because they weren't caught locally
4. Team velocity drops - Time spent debugging "working" code
5. You lose credibility - Claims without evidence are meaningless

The 30 seconds "saved" by not running tests costs 30 minutes debugging later.

THE RULE

Evidence or it didn't happen.

If you didn't run it, you don't know if it works.

If you can't quote the output, you didn't run it.

OUTPUT TEMPLATE

When verifying, use this template:

## Verification Results

### Tests
$ mix test
[paste actual output]
✓ 10 tests, 0 failures

### Compilation
$ mix compile --warnings-as-errors
[paste actual output]
✓ Zero warnings

### Credo
$ mix credo --strict
[paste actual output]
✓ No issues found

### Dialyzer
$ mix dialyzer
[paste actual output]
✓ 0 errors

## Conclusion
All verification steps passed. Task complete.

REMEMBER

"Code doesn't work until you run it and prove it works."

"Assumptions are the mother of all failures."

"If you can't quote the output, you didn't verify it."

RUN. READ. REPORT. Every. Single. Time.