Merge branch 'main' into paper-first-fillout

.gitignore

@@ -17,3 +17,6 @@ paper/src/auto/*
 lib/
 docs/goals/*.md
 PHANTOM.wiki/
+tests/e2e/node_modules/**
+**/auto/*.el
+*.old

Makefile

@@ -11,16 +11,15 @@ PYTEST    := $(VENV)/bin/pytest
 
 .DEFAULT_GOAL := help
 
-all: pdf
+.PHONY: help
-
+help:
-run.webapp:
+	@echo "pdf.build pdf.watch pdf.clean | test.backend test.e2e test.all | web.dev | install | stats.lines"
-	@cd web && npm install && npm run dev
 
 $(BUILDDIR):
 	mkdir -p paper/$(BUILDDIR)
 
-pdf: $(BUILDDIR)
+.PHONY: pdf.build
-	@echo "Concatenating source code..."
+pdf.build: $(BUILDDIR)
 	@bash paper/concat_code.sh
 	@cd $(SRCDIR) && \
 	$(LATEXMK) -pdf -jobname=$(JOBNAME) -f \
@@ -28,32 +27,53 @@ pdf: $(BUILDDIR)
 		-r ../.latexmkrc \
 		-outdir=../$(BUILDDIR) $(TEX)
 
-watch: $(BUILDDIR)
+.PHONY: pdf.watch
+pdf.watch: $(BUILDDIR)
 	@cd $(SRCDIR) && \
 	$(LATEXMK) -pvc -pdf -jobname=$(JOBNAME) -f \
 		-interaction=nonstopmode -file-line-error \
 		-r ../.latexmkrc \
 		-outdir=../$(BUILDDIR) $(TEX)
 
-clean:
+.PHONY: pdf.clean
+pdf.clean:
 	@cd $(SRCDIR) && \
 	$(LATEXMK) -C -jobname=$(JOBNAME) -outdir=../$(BUILDDIR) || true
 	rm -rf paper/$(BUILDDIR)/*
 
+.PHONY: test.backend
+test.backend: $(VENV)
+	$(PYTEST) -v
+
+.PHONY: test.e2e
+test.e2e:
+	@cd tests/e2e && npm install
+	@cd tests/e2e && npx playwright install chromium
+	@timeout 30 bash -c 'until curl -sf http://localhost:5000/health > /dev/null 2>&1; do sleep 1; done' || (echo "Backend not ready" && exit 1)
+	@timeout 30 bash -c 'until curl -sf http://localhost:3000 > /dev/null 2>&1; do sleep 1; done' || (echo "Web app not ready" && exit 1)
+	@cd tests/e2e && npm test
+
+.PHONY: test.all
+test.all: test.backend test.e2e
+
+.PHONY: web.dev
+web.dev:
+	@cd web && npm install && npm run dev
+
 $(VENV):
 	python3 -m venv $(VENV)
 	$(PIP) install --upgrade pip
 
+.PHONY: install
 install: $(VENV)
 	$(PIP) install -r requirements.txt
 
-test: $(VENV)
+.PHONY: stats.lines
-	$(PYTEST) -v
+stats.lines:
-
-count-lines:
 	@find . \( -path '*/node_modules' -o -path '*/.venv' -o -path '*/venv' \) -prune -o \
 	\( -name "*.ts" -o -name "*.py" \) -type f -print0 | xargs -0 cat | wc -l
 
+.PHONY wordcount
 wordcount:
 	@echo "Counting words in main text (excluding appendix)..."
 	@texcount -nosub -total -sum -1 \
@@ -64,4 +84,12 @@ wordcount:
 		$(SRCDIR)/chapters/05-discussion.tex \
 		$(SRCDIR)/chapters/06-conclusion.tex
 
-.PHONY: all pdf clean watch run.webapp install test wordcount
+
+.PHONY: pdf clean watch run.webapp test count-lines all
+pdf: pdf.build
+clean: pdf.clean
+watch: pdf.watch
+run.webapp: web.dev
+test: test.backend
+count-lines: stats.lines
+all: pdf.build

tests/e2e/__init__.py

@@ -0,0 +1 @@
+"""E2E test suite for PHANTOM dynamic pricing pipeline."""

tests/e2e/fixtures.ts

@@ -0,0 +1,17 @@
+import { test as base } from '@playwright/test';
+
+type TestFixtures = {
+  backendUrl: string;
+  pricingUrl: string;
+};
+
+export const test = base.extend<TestFixtures>({
+  backendUrl: async ({}, use) => {
+    await use(process.env.BACKEND_URL || 'http://localhost:5000');
+  },
+  pricingUrl: async ({}, use) => {
+    await use(process.env.PRICING_PROVIDER_URL || 'http://localhost:5001');
+  },
+});
+
+export { expect } from '@playwright/test';

tests/e2e/helpers/api.ts

@@ -0,0 +1,69 @@
+interface PriceResponse {
+  price: number;
+  base_price: number;
+  markup: number;
+  model_version?: string;
+}
+
+export async function fetchPrice(
+  baseUrl: string,
+  productId: string,
+  mode: string = 'simple_surge',
+  sessionId?: string
+): Promise<PriceResponse> {
+  const params = new URLSearchParams();
+  if (sessionId) params.set('sessionId', sessionId);
+
+  const url = `${baseUrl}/api/pricing?mode=${mode}&productId=${productId}&${params}`;
+  const resp = await fetch(url);
+
+  if (!resp.ok) {
+    throw new Error(`Price fetch failed: ${resp.status}`);
+  }
+
+  return resp.json();
+}
+
+export async function waitForPriceChange(
+  baseUrl: string,
+  productId: string,
+  baselinePrice: number,
+  mode: string,
+  sessionId?: string,
+  maxRetries: number = 10,
+  pollInterval: number = 500
+): Promise<PriceResponse> {
+  for (let i = 0; i < maxRetries; i++) {
+    const priceResp = await fetchPrice(baseUrl, productId, mode, sessionId);
+    if (Math.abs(priceResp.price - baselinePrice) > 0.01) {
+      return priceResp;
+    }
+    await new Promise(r => setTimeout(r, pollInterval));
+  }
+
+  throw new Error(`Price did not change after ${maxRetries} retries`);
+}
+
+export async function ingestEvent(
+  baseUrl: string,
+  sessionId: string,
+  event: string,
+  productId?: string,
+  metadata?: Record<string, any>
+): Promise<void> {
+  const resp = await fetch(`${baseUrl}/api/ingest`, {
+    method: 'POST',
+    headers: { 'Content-Type': 'application/json' },
+    body: JSON.stringify({
+      sessionId,
+      event,
+      productId,
+      timestamp: new Date().toISOString(),
+      metadata,
+    }),
+  });
+
+  if (!resp.ok) {
+    throw new Error(`Event ingest failed: ${resp.status}`);
+  }
+}

tests/e2e/helpers/interactions.ts

@@ -0,0 +1,219 @@
+import { Page } from '@playwright/test';
+
+export async function getSessionId(page: Page): Promise<string | null> {
+  const cookies = await page.context().cookies();
+  const sessionCookie = cookies.find(c => c.name === 'phantom_session_id');
+  return sessionCookie?.value || null;
+}
+
+export async function verifySessionConsistency(page: Page, expectedSessionId: string): Promise<boolean> {
+  const currentSessionId = await getSessionId(page);
+  return currentSessionId === expectedSessionId;
+}
+
+export async function createFreshSession(page: Page, storeType: 'hotel' | 'airline' = 'hotel'): Promise<string> {
+  await page.context().clearCookies();
+  await page.goto('/');
+  await page.waitForLoadState('networkidle');
+  await page.waitForTimeout(500);
+
+  const sid = await getSessionId(page);
+  if (!sid) throw new Error('Session not created');
+  return sid;
+}
+
+interface SearchParams {
+  destination?: string;
+  checkIn?: string;
+  guests?: number;
+  rooms?: number;
+  origin?: string;
+  departure?: string;
+  adults?: number;
+}
+
+export async function performSearch(page: Page, params: SearchParams, storeType: 'hotel' | 'airline' = 'hotel' ): Promise<void> {
+  await page.waitForLoadState('networkidle');
+
+  if (storeType === 'hotel') {
+    const destInput = page.locator('input#destination');
+    await destInput.fill(params.destination || 'New York');
+
+    const checkInInput = page.locator('input#checkIn');
+    const checkInDate = params.checkIn || new Date(Date.now() + 7 * 86400000).toISOString().split('T')[0];
+    await checkInInput.fill(checkInDate);
+
+    const searchBtn = page.locator('button:has-text("Search Rooms")');
+    await searchBtn.click();
+  } else {
+    const originDropdown = page.locator('button:has-text("Select origin")').or(
+      page.locator('[id="origin"]').locator('button').first()
+    );
+    await originDropdown.click();
+    await page.waitForTimeout(200);
+    const originOption = page.locator(`button:has-text("${params.origin || 'JFK'}")`).first();
+    await originOption.click();
+    await page.waitForTimeout(200);
+
+    const destDropdown = page.locator('button:has-text("Select destination")').or(
+      page.locator('[id="destination"]').locator('button').first()
+    );
+    await destDropdown.click();
+    await page.waitForTimeout(200);
+    const destOption = page.locator(`button:has-text("${params.destination || 'LAX'}")`).first();
+    await destOption.click();
+    await page.waitForTimeout(200);
+
+    const departInput = page.locator('input#departDate');
+    const departDate = params.departure || new Date(Date.now() + 7 * 86400000).toISOString().split('T')[0];
+    await departInput.fill(departDate);
+
+    const searchBtn = page.locator('button:has-text("Search Flights")');
+    await searchBtn.click();
+  }
+
+  await page.waitForLoadState('networkidle');
+}
+
+export async function selectRandomProduct(page: Page, storeType: 'hotel' | 'airline' = 'hotel'): Promise<string> {
+  await page.waitForLoadState('networkidle');
+
+  const cardClass = storeType === 'hotel' ? '.hotel-card' : '.flight-card';
+  const productCards = page.locator(cardClass);
+
+  const count = await productCards.count();
+  if (count === 0) throw new Error('No products found on listing page');
+
+  const randomIdx = Math.floor(Math.random() * count);
+  return randomIdx.toString();
+}
+
+export async function openProductFromListing(page: Page, productId?: string): Promise<string> {
+  await page.waitForLoadState('networkidle');
+
+  const hotelCards = page.locator('.hotel-card');
+  const flightCards = page.locator('.flight-card');
+
+  const hotelCount = await hotelCards.count();
+  const flightCount = await flightCards.count();
+
+  let productCards;
+  if (hotelCount > 0) {
+    productCards = hotelCards;
+  } else if (flightCount > 0) {
+    productCards = flightCards;
+  } else {
+    throw new Error('No products found on listing page');
+  }
+
+  const count = await productCards.count();
+  const randomIdx = productId ? 0 : Math.floor(Math.random() * count);
+  await productCards.nth(randomIdx).click();
+
+  await page.waitForLoadState('networkidle');
+
+  const url = page.url();
+  const match = url.match(/\/products\/([^/?]+)/);
+  if (!match) throw new Error('Cannot parse product ID from URL after navigation');
+
+  return match[1];
+}
+
+export async function getPriceFromDOM(page: Page): Promise<number> {
+  await page.waitForLoadState('networkidle');
+
+  await page.waitForSelector('.price-amount', { timeout: 15000 }).catch(() => null);
+
+  const priceSelectors = [
+    '.price-amount',
+    '.price-display',
+    '[data-testid="price"]',
+    '[data-price]',
+  ];
+
+  for (const selector of priceSelectors) {
+    const priceEl = page.locator(selector).first();
+    if (await priceEl.count() > 0) {
+      const text = await priceEl.textContent();
+      if (!text) continue;
+
+      const match = text.match(/[\$]?\s*([\d,]+(?:\.\d{2})?)/);
+      if (match) {
+        const priceStr = match[1].replace(/,/g, '');
+        return parseFloat(priceStr);
+      }
+    }
+  }
+
+  const dataPrice = await page.locator('[data-price]').first().getAttribute('data-price').catch(() => null);
+  if (dataPrice) return parseFloat(dataPrice);
+
+  throw new Error('Cannot extract price from DOM');
+}
+
+export async function navigateToProduct(page: Page,productId: string,storeType: 'hotel' | 'airline' = 'hotel'): Promise<void> {
+  await page.goto(`/products/${productId}`);
+  await page.waitForLoadState('networkidle');
+}
+
+export async function viewProductViaFlow(page: Page, storeType: 'hotel' | 'airline' = 'hotel', searchParams?: SearchParams): Promise<string> {
+  const params = new URLSearchParams();
+  params.set('dateIndex', '7');
+
+  if (storeType === 'hotel') {
+    params.set('destination', searchParams?.destination || 'New York');
+    params.set('adults', '2');
+    params.set('rooms', '1');
+  } else {
+    params.set('origin', searchParams?.origin || 'JFK');
+    params.set('destination', searchParams?.destination || 'LAX');
+    params.set('adults', '1');
+    params.set('children', '0');
+    params.set('infants', '0');
+  }
+
+  await page.goto(`/products?${params.toString()}`);
+  await page.waitForLoadState('networkidle');
+
+  const productId = await openProductFromListing(page);
+  await page.waitForTimeout(500);
+  return productId;
+}
+
+export async function rapidViewProductViaFlow(page: Page, count: number, delayMs: number = 100, storeType: 'hotel' | 'airline' = 'hotel'): Promise<string[]> {
+  const productIds: string[] = [];
+
+  for (let i = 0; i < count; i++) {
+    const productId = await viewProductViaFlow(page, storeType);
+    productIds.push(productId);
+
+    await page.waitForTimeout(delayMs);
+  }
+
+  return productIds;
+}
+
+export async function humanLikeViewProduct(page: Page, storeType: 'hotel' | 'airline' = 'hotel'
+): Promise<string> {
+  const productId = await viewProductViaFlow(page, storeType);
+
+  await page.hover('h1');
+  await page.waitForTimeout(800 + Math.random() * 400);
+
+  await page.mouse.wheel(0, 200);
+  await page.waitForTimeout(500 + Math.random() * 300);
+
+  const paragraphs = await page.locator('p').all();
+  if (paragraphs.length > 0) {
+    await paragraphs[0].hover();
+    await page.waitForTimeout(600 + Math.random() * 400);
+  }
+
+  return productId;
+}
+
+export async function addToCart(page: Page): Promise<void> {
+  const addBtn = page.locator('button:has-text("Add to Cart")');
+  await addBtn.click();
+  await page.waitForTimeout(500);
+}

tests/e2e/helpers/kafka.ts

@@ -0,0 +1,39 @@
+interface InteractionEvent {
+  sessionId: string;
+  event: string;
+  productId?: string;
+  timestamp: string;
+  metadata?: Record<string, any>;
+}
+
+const dumpKafkaTopic = async (backendUrl: string, topic: string) => {
+  const resp = await fetch(`${backendUrl}/api/kafka/dump?topic=${topic}`);
+  if (!resp.ok) throw new Error(`Kafka dump failed: ${resp.status}`);
+  const { messages = [] } = await resp.json();
+  return messages as any[];
+};
+
+export const waitForInteractionEvent = async (
+  backendUrl: string,
+  sessionId: string,
+  eventType: string,
+  maxRetries = 10,
+  pollInterval = 500
+): Promise<InteractionEvent | null> => {
+  for (let i = 0; i < maxRetries; i++) {
+    const msgs = await dumpKafkaTopic(backendUrl, "user-interactions");
+    const hit = msgs.find(m => m.sessionId === sessionId && m.event === eventType);
+    if (hit) return hit as InteractionEvent;
+    await new Promise<void>(r => setTimeout(r, pollInterval));
+  }
+  return null;
+};
+
+export const countProductViews = async (backendUrl: string, productId: string) =>
+  (await dumpKafkaTopic(backendUrl, "user-interactions")).reduce(
+    (n, m) => n + (m.productId === productId && m.event === "view_item_page" ? 1 : 0),
+    0
+  );
+
+export const getSessionEvents = async (backendUrl: string, sessionId: string) =>
+  (await dumpKafkaTopic(backendUrl, "user-interactions")).filter(m => m.sessionId === sessionId);

tests/e2e/package.json

@@ -0,0 +1,19 @@
+{
+  "name": "e2e",
+  "version": "1.0.0",
+  "main": "index.js",
+  "scripts": {
+    "test": "playwright test",
+    "test:ui": "playwright test --ui",
+    "test:debug": "playwright test --debug"
+  },
+  "keywords": [],
+  "author": "",
+  "license": "ISC",
+  "description": "",
+  "devDependencies": {
+    "@playwright/test": "^1.57.0",
+    "@types/node": "^25.0.6",
+    "typescript": "^5.9.3"
+  }
+}

tests/e2e/playwright.config.ts

@@ -0,0 +1,25 @@
+import { defineConfig, devices } from '@playwright/test';
+
+export default defineConfig({
+  testDir: './scenarios',
+  fullyParallel: true,
+  forbidOnly: !!process.env.CI,
+  retries: 0,
+  workers: 5,
+  reporter: 'list',
+  use: {
+    baseURL: process.env.WEB_URL || 'http://localhost:3000',
+    trace: 'retain-on-failure',
+    screenshot: 'only-on-failure',
+  },
+  timeout: 60000,
+  expect: {
+    timeout: 10000,
+  },
+  projects: [
+    {
+      name: 'chromium',
+      use: { ...devices['Desktop Chrome'] },
+    },
+  ],
+});

tests/e2e/scenarios/session-aware.spec.ts

@@ -0,0 +1,156 @@
+import { test, expect } from '../fixtures';
+import {
+  createFreshSession,
+  viewProductViaFlow,
+  rapidViewProductViaFlow,
+  humanLikeViewProduct,
+  getPriceFromDOM,
+  verifySessionConsistency,
+  addToCart,
+} from '../helpers/interactions';
+import { getSessionEvents } from '../helpers/kafka';
+
+test.describe('SessionAwarePricer E2E', () => {
+  const STORE_TYPE = 'hotel';
+
+  test('baseline: human-like behavior maintains base price', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productId1 = await humanLikeViewProduct(page, STORE_TYPE);
+    const baselinePrice = await getPriceFromDOM(page);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+
+    await page.waitForTimeout(1500);
+
+    const productId2 = await humanLikeViewProduct(page, STORE_TYPE);
+    const secondPrice = await getPriceFromDOM(page);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+
+    expect(Math.abs(secondPrice - baselinePrice) / baselinePrice).toBeLessThan(0.1);
+  });
+
+  test('agent detection: rapid robot-like behavior increases price', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productId = await viewProductViaFlow(page, STORE_TYPE);
+    const baselinePrice = await getPriceFromDOM(page);
+
+    await page.waitForTimeout(500);
+
+    await rapidViewProductViaFlow(page, 8, 100, STORE_TYPE);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+
+    await page.waitForTimeout(2500);
+
+    const events = await getSessionEvents(backendUrl, sessionId);
+    expect(events.length).toBeGreaterThanOrEqual(8);
+
+    await page.goto(`/products/${productId}`);
+    await page.waitForLoadState('networkidle');
+    const agentPrice = await getPriceFromDOM(page);
+
+    expect(agentPrice).toBeGreaterThan(baselinePrice);
+    expect((agentPrice - baselinePrice) / baselinePrice).toBeGreaterThan(0.01);
+  });
+
+  test('velocity threshold: high event rate triggers detection', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productId = await viewProductViaFlow(page, STORE_TYPE);
+    const baselinePrice = await getPriceFromDOM(page);
+
+    const startTime = Date.now();
+    await rapidViewProductViaFlow(page, 10, 80, STORE_TYPE);
+    const duration = (Date.now() - startTime) / 1000;
+
+    const eventsPerSec = 10 / duration;
+    expect(eventsPerSec).toBeGreaterThan(2.0);
+
+    await page.waitForTimeout(2000);
+
+    await page.goto(`/products/${productId}`);
+    await page.waitForLoadState('networkidle');
+    const agentPrice = await getPriceFromDOM(page);
+
+    expect(agentPrice).toBeGreaterThan(baselinePrice);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+  });
+
+  test('cart ratio: high cart/view ratio signals intent', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productId = await viewProductViaFlow(page, STORE_TYPE);
+    const baselinePrice = await getPriceFromDOM(page);
+
+    await page.waitForTimeout(500);
+    await addToCart(page);
+
+    await page.waitForTimeout(2000);
+
+    await page.goto(`/products/${productId}`);
+    await page.waitForLoadState('networkidle');
+    const cartPrice = await getPriceFromDOM(page);
+
+    expect(cartPrice).toBeGreaterThanOrEqual(baselinePrice);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+  });
+
+  test('mixed behavior: occasional fast actions tolerated', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productId1 = await humanLikeViewProduct(page, STORE_TYPE);
+    const baselinePrice = await getPriceFromDOM(page);
+
+    await page.waitForTimeout(1200);
+
+    await rapidViewProductViaFlow(page, 2, 150, STORE_TYPE);
+
+    await page.waitForTimeout(1500);
+    await humanLikeViewProduct(page, STORE_TYPE);
+    const finalPrice = await getPriceFromDOM(page);
+
+    expect(Math.abs(finalPrice - baselinePrice) / baselinePrice).toBeLessThan(0.3);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+  });
+
+  test('session isolation: agent behavior in one session does not affect others', async ({
+    page,
+    context,
+    backendUrl,
+  }) => {
+    const sessionIdA = await createFreshSession(page, STORE_TYPE);
+    const productId = await viewProductViaFlow(page, STORE_TYPE);
+    const basePrice = await getPriceFromDOM(page);
+
+    await rapidViewProductViaFlow(page, 10, 100, STORE_TYPE);
+    await page.waitForTimeout(2000);
+
+    await page.goto(`/products/${productId}`);
+    await page.waitForLoadState('networkidle');
+    const agentPrice = await getPriceFromDOM(page);
+    expect(agentPrice).toBeGreaterThan(basePrice * 0.99);
+
+    const page2 = await context.newPage();
+    const sessionIdB = await createFreshSession(page2, STORE_TYPE);
+
+    await page2.goto(`/products/${productId}`);
+    await page2.waitForLoadState('networkidle');
+    const cleanPrice = await getPriceFromDOM(page2);
+
+    expect(Math.abs(cleanPrice - basePrice) / basePrice).toBeLessThan(0.1);
+    expect(sessionIdA).not.toBe(sessionIdB);
+  });
+
+  test('session persistence: session ID maintained across views', async ({ page }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    await viewProductViaFlow(page, STORE_TYPE);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+
+    await viewProductViaFlow(page, STORE_TYPE);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+
+    await viewProductViaFlow(page, STORE_TYPE);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+  });
+});

tests/e2e/scenarios/surge-pricing.spec.ts

@@ -0,0 +1,111 @@
+import { test, expect } from '../fixtures';
+import {
+  createFreshSession,
+  viewProductViaFlow,
+  rapidViewProductViaFlow,
+  getPriceFromDOM,
+  verifySessionConsistency,
+} from '../helpers/interactions';
+import { waitForInteractionEvent, countProductViews } from '../helpers/kafka';
+
+test.describe('SimpleSurgePricer E2E', () => {
+  const STORE_TYPE = 'hotel';
+
+  test('baseline: initial price equals base price', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productId = await viewProductViaFlow(page, STORE_TYPE);
+    const price = await getPriceFromDOM(page);
+
+    expect(price).toBeGreaterThan(0);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+  });
+
+  test('surge: rapid views trigger price increase', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productId = await viewProductViaFlow(page, STORE_TYPE);
+    const baselinePrice = await getPriceFromDOM(page);
+
+    await rapidViewProductViaFlow(page, 5, 200, STORE_TYPE);
+
+    await page.waitForTimeout(2000);
+
+    const evt = await waitForInteractionEvent(backendUrl, sessionId, 'view_item_page');
+    expect(evt).not.toBeNull();
+
+    const viewCount = await countProductViews(backendUrl, productId);
+    expect(viewCount).toBeGreaterThanOrEqual(5);
+
+    await page.goto(`/products/${productId}`);
+    await page.waitForLoadState('networkidle');
+    const surgedPrice = await getPriceFromDOM(page);
+
+    expect(surgedPrice).toBeGreaterThan(baselinePrice);
+    expect((surgedPrice - baselinePrice) / baselinePrice).toBeGreaterThan(0.01);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+  });
+
+  test('threshold: price unchanged below threshold', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productId = await viewProductViaFlow(page, STORE_TYPE);
+    const baselinePrice = await getPriceFromDOM(page);
+
+    await rapidViewProductViaFlow(page, 2, 300, STORE_TYPE);
+
+    await page.waitForTimeout(1500);
+
+    await page.goto(`/products/${productId}`);
+    await page.waitForLoadState('networkidle');
+    const currentPrice = await getPriceFromDOM(page);
+
+    expect(Math.abs(currentPrice - baselinePrice) / baselinePrice).toBeLessThan(0.05);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+  });
+
+  test('window: surge decays after window expires', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productId = await viewProductViaFlow(page, STORE_TYPE);
+    const baselinePrice = await getPriceFromDOM(page);
+
+    await rapidViewProductViaFlow(page, 5, 150, STORE_TYPE);
+
+    await page.waitForTimeout(1500);
+
+    await page.goto(`/products/${productId}`);
+    await page.waitForLoadState('networkidle');
+    const surgedPrice = await getPriceFromDOM(page);
+    expect(surgedPrice).toBeGreaterThan(baselinePrice);
+
+    await page.waitForTimeout(12000);
+
+    await page.goto(`/products/${productId}`);
+    await page.waitForLoadState('networkidle');
+    const decayedPrice = await getPriceFromDOM(page);
+    expect(decayedPrice).toBeLessThan(surgedPrice);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+  });
+
+  test('isolation: different products have independent surge', async ({ page, backendUrl }) => {
+    const sessionId = await createFreshSession(page, STORE_TYPE);
+
+    const productIdA = await viewProductViaFlow(page, STORE_TYPE);
+    const basePriceA = await getPriceFromDOM(page);
+
+    await rapidViewProductViaFlow(page, 5, 200, STORE_TYPE);
+    await page.waitForTimeout(2000);
+
+    await page.goto(`/products/${productIdA}`);
+    await page.waitForLoadState('networkidle');
+    const surgedPriceA = await getPriceFromDOM(page);
+
+    const productIdB = await viewProductViaFlow(page, STORE_TYPE);
+    const priceB = await getPriceFromDOM(page);
+
+    expect(surgedPriceA).toBeGreaterThan(basePriceA * 0.99);
+    expect(productIdA).not.toBe(productIdB);
+    expect(await verifySessionConsistency(page, sessionId)).toBeTruthy();
+  });
+});

tests/e2e/tsconfig.json

@@ -0,0 +1,15 @@
+{
+  "compilerOptions": {
+    "target": "ES2022",
+    "module": "commonjs",
+    "lib": ["ES2022"],
+    "strict": true,
+    "esModuleInterop": true,
+    "skipLibCheck": true,
+    "forceConsistentCasingInFileNames": true,
+    "resolveJsonModule": true,
+    "types": ["node", "@playwright/test"]
+  },
+  "include": ["**/*.ts"],
+  "exclude": ["node_modules"]
+}