add-diagnostic-test

name	add-diagnostic-test
description	Create a new diagnostic parity test case. Use when the user asks to add a diagnostic test, create a new `tasks/diagnostic_tests/cases/<name>` case, or capture a false positive/false negative against npm `svelte/compiler` before implementation.

Add Diagnostic Test

Capture utility — not part of the PARITY chain. Creates a persistent diagnostic case for feature-first work. Do NOT use when you already have a dig finding — that work lives under tasks/diagnostic_tests/cases/ and is scoped by /dig. Use this skill only when registering a fresh, standalone diagnostic case before implementation.

1) Validate the name

snake_case. Stop if tasks/diagnostic_tests/cases/<name>/ exists.

2) Create a minimal case

Add tasks/diagnostic_tests/cases/<name>/case.svelte — the smallest component isolating one diagnostic behavior. Extend an existing case instead only when it already covers the same diagnostic code or syntax family and its case.svelte stays small.

Add config.json only when the diagnostic depends on compile options.

3) Generate reference snapshots

Run:

just generate

Creates case-svelte.json from npm svelte/compiler. Never hand-edit case-svelte.json or case-rust.json.

4) Register the test

Add #[rstest] case to tasks/diagnostic_tests/test_diagnostics.rs:

#[rstest]
fn <name>() {
    assert_diagnostics("<name>");
}

5) Run the test

just test-diagnostic-case <name>

Test writes case-rust.json for human comparison. Failure normal in test-first workflow. Report mismatch clearly. Do not "fix" reference snapshots.

6) Report

Include:

• what diagnostic test covers
• pass/fail
• mismatch summary if fails
• next recommended command, usually /diagnose-diagnostics or /port specs/<feature>.md