test(hq): golden fidelity — preview HTML byte-identical to the PDF's HTML

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

apps/hq/test/preview-fidelity.test.ts

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+// apps/hq/test/preview-fidelity.test.ts
+import { describe, it, expect, afterAll } from 'vitest'
+import express from 'express'
+import { openDb } from '../src/db'
+import { seedIfEmpty } from '../src/seed'
+import { createStaff } from '../src/auth'
+import { createClient, getClient } from '../src/repos-clients'
+import { createModule, setPrice } from '../src/repos-modules'
+import { createDraft } from '../src/repos-documents'
+import { documentHtml } from '../src/templates'
+import { apiRouter } from '../src/api'
+
+function companyMap(db: any): Record<string, string> {
+  const rows = db.prepare(`SELECT key, value FROM setting WHERE key LIKE 'company.%'`).all() as { key: string; value: string }[]
+  return Object.fromEntries(rows.map((r) => [r.key, r.value]))
+}
+
+describe('preview fidelity (string identity with the PDF path)', () => {
+  const db = openDb(':memory:'); seedIfEmpty(db)
+  createStaff(db, { email: 'owner@test.in', displayName: 'Owner', role: 'owner', password: 'owner-password' })
+  const c = createClient(db, 'u1', { name: 'Acme', code: 'ACME', stateCode: '32', address: 'Kochi', gstin: '32ABCDE1234F1Z9' })
+  const m = createModule(db, 'u1', { code: 'POS', name: 'POS Billing', quoteContent: ['Cloud POS', 'GST filing'] })
+  setPrice(db, 'u1', { moduleId: m.id, kind: 'yearly', pricePaise: 10_000_00, effectiveFrom: '2026-04-01' })
+  const app = express(); app.use(express.json()); app.locals['db'] = db; app.use('/api', apiRouter(db))
+  const server = app.listen(0)
+  const base = `http://localhost:${(server.address() as { port: number }).port}/api`
+  afterAll(() => server.close())
+
+  it('preview.html === documentHtml the /pdf route would feed renderPdf', async () => {
+    const input = { docType: 'INVOICE', clientId: c.id, terms: 'Net 15',
+      lines: [{ moduleId: m.id, qty: 2, kind: 'yearly' }] }
+    // The fixture draft: exactly what /documents/:id/pdf renders (un-issued draft, docNo=null).
+    const fixture = createDraft(db, 'u1', input)
+    const expected = documentHtml(fixture, getClient(db, c.id)!, companyMap(db))
+
+    const token = (await (await fetch(`${base}/auth/login`, { method: 'POST', headers: { 'content-type': 'application/json' }, body: JSON.stringify({ email: 'owner@test.in', password: 'owner-password' }) })).json() as any).token
+    const res = await fetch(`${base}/documents/preview`, { method: 'POST', headers: { 'content-type': 'application/json', authorization: `Bearer ${token}` }, body: JSON.stringify(input) })
+    const out = await res.json() as any
+
+    expect(out.html).toBe(expected) // one renderer — no drift possible
+  })
+})