DPE Testing Strategy

The DPE follows a 4-layer testing pyramid, adapted from the Sipi testing strategy. Target distribution: ~50% unit, ~30% E2E, ~15% snapshot, ~5% fuzz.

Testing Pyramid

          ╱╲
         ╱  ╲         Layer 4: Fuzz Testing (nightly CI)
        ╱────╲        cargo-fuzz, corpus persisted
       ╱      ╲
      ╱  E2E   ╲     Layer 3: E2E Tests (Playwright)
     ╱──────────╲     Tab switching, search, accessibility (axe-core)
    ╱            ╲
   ╱  Snapshots   ╲   Layer 2: Snapshot Tests (insta)
  ╱────────────────╲   SSR output, SSE fragments, ARIA attributes
 ╱                  ╲
╱    Unit Tests      ╲ Layer 1: Unit Tests (cargo test)
╱────────────────────╲ Fragment handlers, OAI protocol, domain logic

Layer 1: Unit Tests

• Location: #[cfg(test)] modules in each crate
• Runner: cargo test --workspace
• Scope: Fragment handlers, OAI protocol, domain types, data loading, filtering/pagination
• Crate: dpe-core tests run independently — cargo test -p dpe-core

Layer 2: Snapshot Tests (insta)

• Dependency: insta with yaml and filters features
• Location: Adjacent snapshots/ directories
• CI: Set INSTA_UPDATE=new so failures produce .snap.new artifacts for review
• Scope: SSR output, SSE fragment response bodies, ARIA attributes

Layer 3: E2E Tests (Playwright)

• Location: modules/dpe/web-e2e-tests/
• Runner: npx playwright test
• Scope: Tab switching, search autocomplete, scroll preservation, accessibility (axe-core), visual regression
• Accessibility: Full-page axe-core scans against WCAG 2.1 AA

Layer 4: Fuzz Testing

• Tool: cargo-fuzz (nightly Rust)
• Schedule: Nightly CI, 10 minutes per target
• Targets: Tab name validation, SSE response construction, query parameter parsing
• Corpus: Persisted between runs

CI Pipeline Budget

Target: ≤ 10 minutes wall-clock per PR.

Parallel job group 1 (~2 min):
  cargo fmt --check
  cargo clippy --all-targets -Dwarnings
  cargo-deny check

Parallel job group 2 (~5 min):
  cargo nextest run --workspace
  cargo leptos build --release
  cargo-llvm-cov (coverage → Codecov)

Parallel job group 3 (~5 min):
  Playwright E2E tests
  axe-core accessibility scans
  Lighthouse CI performance budgets

Testing Conventions

Test naming: Use descriptive names following the test_{what}_{condition}_{expected} pattern. For example: test_parse_project_missing_title_returns_error.

Test locations:

• Unit tests: In-crate #[cfg(test)] modules or adjacent _tests.rs files
• Snapshot files: .snap files committed to git in snapshots/ directories
• E2E tests: web-e2e-tests/ for DPE, playground-e2e-tests/ for Mosaic
• Fuzz corpus: Persisted in the repository under fuzz/corpus/

Test file naming: {feature}_tests.rs for Rust, {feature}.spec.ts for Playwright.

Snapshot tests: Use the insta crate. Use with_settings! for scrubbing dynamic values (timestamps, IDs). CI runs with INSTA_UPDATE=new so unexpected changes produce .snap.new files for review.