astro44/test-create-fixture

test-create-fixture - Component Test Fixture & Spec Creator

Creates HTML test fixture files AND Playwright spec files for UI components. Used by dev agents during TDD to create isolated test pages before implementation.

Web Platform Enhancement: For web projects, this skill creates BOTH the fixture HTML AND the Playwright spec file to avoid silent failures from missing specs.

Input Schema

{
  "project_dir": "/path/to/project",
  "ticket_id": "TICKET-XXX_A.1",
  "component_path": "src/components/impact/MetricCard.js",
  "fixture_path": "src/tests/metric-card.html",
  "spec_path": "tests/metric-card.spec.js",
  "component_name": "MetricCard",
  "component_class": "MetricCard",
  "platform": "web",
  "acceptance_criteria": [
    {"id": "AC-001", "description": "Counter animates from 0 to target"},
    {"id": "AC-002", "description": "Displays unit label correctly"}
  ]
}

Note: spec_path is REQUIRED for web platform. If not provided, derive from fixture_path:

• src/tests/metric-card.html → tests/metric-card.spec.js

CRITICAL: Use Absolute URL Paths (NOT Relative)

NEVER use relative paths like ../../ in fixture imports.

The server runs from src/ directory, making src/ the web root:

• src/tests/*.html → served at /tests/*.html
• src/components/**/*.js → served at /components/**/*.js

WHY relative paths break:

fixture_path: src/tests/metric-card.html
component_path: src/components/impact/MetricCard.js

WRONG: ../../components/impact/MetricCard.js
       → resolves to project_root/components/impact/MetricCard.js (OUTSIDE src/)
       → FILE NOT FOUND

RIGHT: /components/impact/MetricCard.js
       → resolves from server root (src/) to src/components/impact/MetricCard.js
       → FILE FOUND ✓

Instructions

1. Locate Templates

# Fixture template location (in order of priority):
# 1. Project-specific: {project_dir}/templates/tests/component-fixture.html
# 2. Harness: {project_dir}/harness/templates/component-fixture.html
# 3. Global: templates/project/tests/web/component-fixture.template.html

# Spec template location (web platform only):
# 1. Project-specific: {project_dir}/templates/tests/component.spec.template.js
# 2. Global: templates/project/tests/web/component.spec.template.js

2. Process Template Variables

Replace mustache-style variables in templates:

Shared Variables (Fixture + Spec)

| Variable | Source | Example | |----------|--------|---------| | {{TICKET_ID}} | input.ticket_id | TICKET-OXY-003_A.1 | | {{COMPONENT_NAME}} | input.component_name | MetricCard | | {{COMPONENT_CLASS}} | input.component_class | MetricCard | | {{#ACCEPTANCE_CRITERIA}} | Loop over ACs | Creates test sections | | {{AC_ID}} | Each AC ID | AC-001 | | {{AC_DESCRIPTION}} | Each AC description | Counter animates... |

Fixture-Specific Variables

| Variable | Source | Example | |----------|--------|---------| | {{COMPONENT_PATH}} | Absolute URL from server root | /components/impact/MetricCard.js | | {{COMPONENT_CSS}} | CSS absolute URL | /styles/metric-card.css | | {{COMPONENT_OPTIONS}} | Default init options | {} or from ticket | | {{COMPONENT_SELECTOR}} | data-* attribute name (kebab-case) | circular-progress |

Spec-Specific Variables (Web Platform)

| Variable | Source | Example | |----------|--------|---------| | {{SPEC_FILENAME}} | Basename of spec_path | metric-card.spec.js | | {{FIXTURE_FILENAME}} | Basename of fixture_path | metric-card.html |

3. Calculate Absolute URL Paths

CRITICAL: Check for import_prefix in context first!

The import_prefix context variable tells you if the server needs a path prefix (e.g., /src).

// FIRST: Check if import_prefix is provided in context
// If import_prefix = "/src", paths need the /src prefix
// If import_prefix = "", server serves from src/ directly

function toAbsoluteUrl(filePath, importPrefix) {
  // Remove src/ prefix if present to get relative path
  let relativePath = filePath;
  if (filePath.startsWith('src/')) {
    relativePath = filePath.slice(4); // Remove 'src/'
  }

  // Apply import_prefix if provided (e.g., "/src" when server runs from project root)
  if (importPrefix) {
    return importPrefix + '/' + relativePath;
  }

  // Default: assume server runs from src/, no prefix needed
  return '/' + relativePath;
}

// Examples WITH import_prefix="/src" (server at project root):
// src/components/impact/MetricCard.js → /src/components/impact/MetricCard.js
// src/styles/metric-card.css → /src/styles/metric-card.css

// Examples WITHOUT import_prefix (server at src/):
// src/components/impact/MetricCard.js → /components/impact/MetricCard.js
// src/styles/metric-card.css → /styles/metric-card.css

Always check context for import_prefix before generating import paths!

4. Generate AC Test Sections

For each acceptance criterion, create a test section:

<div class="test-section" id="test-AC-001">
  <h2>AC-001: Counter animates from 0 to target</h2>
  <div data-test-scenario="ac-001"></div>
</div>

5. Write Fixture File

// Ensure directory exists
const fixtureDir = path.dirname(fixturePath);
await fs.mkdir(fixtureDir, { recursive: true });

// Write processed template
await fs.writeFile(fixturePath, processedTemplate);

6. Write Spec File (Web Platform Only)

CRITICAL: For web platform, ALWAYS create the spec file alongside the fixture.

This step prevents silent failures where the fixture is created but the spec is missing, causing TDD verification to fail.

// Derive spec path if not provided
function deriveSpecPath(fixturePath) {
  // src/tests/metric-card.html → tests/metric-card.spec.js
  const basename = path.basename(fixturePath, '.html');
  return `tests/${basename}.spec.js`;
}

// Ensure spec directory exists
const specPath = input.spec_path || deriveSpecPath(input.fixture_path);
const specDir = path.dirname(specPath);
await fs.mkdir(specDir, { recursive: true });

// Process spec template with variables
const specTemplate = await loadTemplate('component.spec.template.js');
const processedSpec = specTemplate
  .replace(/\{\{TICKET_ID\}\}/g, input.ticket_id)
  .replace(/\{\{COMPONENT_NAME\}\}/g, input.component_name)
  .replace(/\{\{COMPONENT_CLASS\}\}/g, input.component_class)
  .replace(/\{\{SPEC_FILENAME\}\}/g, path.basename(specPath))
  .replace(/\{\{FIXTURE_FILENAME\}\}/g, path.basename(input.fixture_path));

// Process acceptance criteria loop
const acTests = input.acceptance_criteria.map(ac =>
  `  test('${ac.id}: ${ac.description}', async ({ page }) => {
    const status = page.locator('#test-status');
    await expect(status).toHaveClass(/success/);
    // TODO: Add specific assertions for ${ac.id}
  });`
).join('\n\n');
processedSpec = processedSpec.replace(/\{\{#ACCEPTANCE_CRITERIA\}\}[\s\S]*?\{\{\/ACCEPTANCE_CRITERIA\}\}/g, acTests);

// Write spec file
await fs.writeFile(path.join(input.project_dir, specPath), processedSpec);

Output Format

{
  "skill": "test-create-fixture",
  "status": "success|failure",
  "fixture_created": "src/tests/metric-card.html",
  "spec_created": "tests/metric-card.spec.js",
  "fixture_template_used": "templates/project/tests/web/component-fixture.template.html",
  "spec_template_used": "templates/project/tests/web/component.spec.template.js",
  "platform": "web",
  "variables_replaced": {
    "TICKET_ID": "TICKET-OXY-003_A.1",
    "COMPONENT_NAME": "MetricCard",
    "COMPONENT_PATH": "/components/impact/MetricCard.js",
    "ACCEPTANCE_CRITERIA": 2
  },
  "test_sections": ["AC-001", "AC-002"],
  "warnings": [],
  "next_action": "validate_fixture"
}

IMPORTANT: For web platform, both fixture_created AND spec_created must be present for success. If either file fails to create, return status: "failure" with appropriate error message.

Happy Path Only (CRITICAL)

Initial fixtures focus on happy path ONLY. Edge case testing is deferred to later phases.

What to Include (Happy Path)

• Primary data loading with valid endpoints
• Standard component initialization
• Default configurations
• Expected successful responses

What to Defer (Edge Cases)

• Missing file/endpoint tests (AC descriptions mentioning "missing", "invalid", "error handling")
• Error recovery scenarios
• Timeout/failure handling
• Malformed input validation

Handling Edge Case ACs

When an AC describes edge case behavior (missing files, errors, invalid data), do NOT test it directly. Instead:

// AC-3: "No runtime errors when data file is missing"
// DEFERRED - mark as deferred, don't request missing file
setOutput('ac-3', JSON.stringify({
  status: 'deferred',
  note: 'Edge case test deferred until happy path validated'
}, null, 2));

Rationale: Early TDD phases validate that components work correctly with valid inputs. Edge case testing requires additional infrastructure (mock servers, error injection) that may not exist yet.

Fixture Requirements

The generated fixture MUST include:

1. Isolated component - Only the target component, no page context
2. Real imports - Import from actual src/ path, not copies
3. Test sections per AC - Each acceptance criterion gets a section
4. data-testid attributes - For Playwright selection
5. Status indicator - Shows init success/failure (#test-status.success/.error)
6. Playwright hooks - CRITICAL for test access:

Required Window Globals (CRITICAL)

// Set SYNCHRONOUSLY (before async init) for browser timing consistency
window.__testModule = {
  ComponentClass,        // The class constructor
  initComponentFactory,  // Factory function if available
  ...otherExports        // All named exports from module
};

// Set AFTER async init completes
window.__testInstances = [...];  // Array of initialized instances
window.__getTestInstance = () => instances[0];
window.__getTestInstances = () => instances;
window.__isInitialized = () => initComplete && !error;
window.__getInitError = () => initError;

Why __testModule is CRITICAL:

• ES6 module loading timing varies by browser (Chromium is slower)
• Tests use page.waitForFunction(() => window.__testModule) to wait for module
• If not set synchronously, tests fail with race conditions
• Chromium especially affected (19 failures vs WebKit's 4)

Null-Return Handling (CRITICAL - Prevents False Positives)

Problem: Many components return null on failure instead of throwing exceptions. Fixtures that only use try/catch will show "success" even when initialization failed.

Solution: Always check for null returns in the initialization IIFE:

(async () => {
    try {
        const instance = await createComponent(container);

        // CRITICAL: Check for null return (component failed internally)
        if (!instance) {
            initError = new Error('Component returned null - initialization failed');
            statusEl.textContent = 'Error: Component failed to initialize';
            statusEl.className = 'error';
            window.__isInitialized = () => false;
            window.__getInitError = () => initError;
            return;
        }

        // Success path
        instances.push(instance);
        window.__testInstances = instances;
        statusEl.textContent = 'Component initialized successfully';
        statusEl.className = 'success';
        window.__isInitialized = () => true;
    } catch (error) {
        initError = error;
        console.error('Component initialization error:', error);
        statusEl.textContent = 'Error: ' + error.message;
        statusEl.className = 'error';
        window.__isInitialized = () => false;
        window.__getInitError = () => initError;
    }
})();

Why This Matters for Fallback Tests: When testing graceful degradation (e.g., "shows fallback when Mapbox fails"):

// In spec file:
test('AC-6: Shows fallback when dependency fails', async ({ page }) => {
    // Block the dependency
    await page.route('**/mapbox-gl.js', route => route.abort());
    await page.reload({ waitUntil: 'networkidle' });

    // Wait for error state (fixture sets .error class on null return)
    await page.waitForSelector('#test-status.error', { timeout: 5000 });

    // Verify fallback UI rendered
    await expect(page.locator('.component-fallback')).toBeVisible();
});

Without null-return handling, this test fails because the fixture shows "success" with 0 instances instead of "error".

Example Generated Fixture

<!DOCTYPE html>
<html lang="en">
<head>
  <title>MetricCard Test - TICKET-OXY-003_A.1</title>
  <!-- ABSOLUTE URLs - server root is src/ -->
  <link rel="stylesheet" href="/styles/impact/metric-card.css">
</head>
<body>
  <div class="test-container">
    <h1>MetricCard Test</h1>

    <div class="test-section" id="test-AC-001">
      <h2>AC-001: Counter animates from 0 to target</h2>
      <div data-testid="ac-001-container"></div>
    </div>

    <div class="test-section" id="test-AC-002">
      <h2>AC-002: Displays unit label correctly</h2>
      <div data-testid="ac-002-container"></div>
    </div>

    <div id="test-status">Loading...</div>
  </div>

  <script type="module">
    // ABSOLUTE URL - NOT relative! Server root is src/
    import { MetricCard } from '/components/impact/MetricCard.js';
    // ... initialization code
  </script>
</body>
</html>

Token Efficiency

• Template-based generation (no LLM needed for structure)
• ~2-5 second execution
• Returns ready-to-use HTML fixture AND Playwright spec (web platform)
• Self-sufficient for basic TDD scaffolding - no agent fallback needed for standard cases

Platform Detection

// Determine platform from input or project config
function getPlatform(input) {
  if (input.platform) return input.platform;

  // Check fixture path pattern
  if (input.fixture_path.endsWith('.html')) return 'web';
  if (input.fixture_path.includes('widget_test')) return 'flutter';
  if (input.fixture_path.includes('XCTest')) return 'ios';

  // Default to web for unknown
  return 'web';
}

// Only create spec for web platform
const platform = getPlatform(input);
if (platform === 'web') {
  // Create both fixture AND spec
} else {
  // Other platforms: fixture only (platform-specific test frameworks)
}