docfast/src/__tests__/billing-edge-cases.test.ts

import { describe, it, expect, vi, beforeEach, afterEach } from "vitest";
import express from "express";
import request from "supertest";

// Mock Stripe before importing billing router
vi.mock("stripe", () => {
  const mockStripe = {
    checkout: {
      sessions: {
        create: vi.fn(),
        retrieve: vi.fn(),
      },
    },
    webhooks: {
      constructEvent: vi.fn(),
    },
    products: {
      search: vi.fn(),
      create: vi.fn(),
    },
    prices: {
      list: vi.fn(),
      create: vi.fn(),
    },
    subscriptions: {
      retrieve: vi.fn(),
    },
  };
  return { default: vi.fn(function() { return mockStripe; }), __mockStripe: mockStripe };
});

let app: express.Express;
let mockStripe: any;

beforeEach(async () => {
  vi.clearAllMocks();
  vi.resetModules();

  process.env.STRIPE_SECRET_KEY = "sk_test_fake";
  process.env.STRIPE_WEBHOOK_SECRET = "whsec_test_fake";

  const stripeMod = await import("stripe");
  mockStripe = (stripeMod as any).__mockStripe;

  // Default: product search returns existing product+price
  mockStripe.products.search.mockResolvedValue({ data: [{ id: "prod_TygeG8tQPtEAdE" }] });
  mockStripe.prices.list.mockResolvedValue({ data: [{ id: "price_123" }] });

  const { createProKey, findKeyByCustomerId, downgradeByCustomer, updateEmailByCustomer } = await import("../services/keys.js");
  vi.mocked(createProKey).mockResolvedValue({ key: "pro-key-123", tier: "pro", email: "test@test.com", createdAt: new Date().toISOString() } as any);
  vi.mocked(findKeyByCustomerId).mockResolvedValue(null);
  vi.mocked(downgradeByCustomer).mockResolvedValue(undefined as any);
  vi.mocked(updateEmailByCustomer).mockResolvedValue(true as any);

  const { billingRouter } = await import("../routes/billing.js");
  app = express();
  app.use("/v1/billing/webhook", express.raw({ type: "application/json" }));
  app.use(express.json());
  app.use("/v1/billing", billingRouter);
});

afterEach(() => {
  vi.restoreAllMocks();
});

describe("Billing Edge Cases - Branch Coverage Improvements", () => {
  describe("Line 231-233: checkout.session.completed webhook - catch block when session.retrieve fails", () => {
    it("RED: should handle error when retrieving session line_items throws", async () => {
      // Setup webhook event
      mockStripe.webhooks.constructEvent.mockReturnValue({
        type: "checkout.session.completed",
        data: {
          object: {
            id: "cs_retrieve_error",
            customer: "cus_retrieve_error",
            customer_details: { email: "error@test.com" },
          },
        },
      });

      // Mock: session.retrieve throws an error (network timeout, Stripe API error, etc.)
      mockStripe.checkout.sessions.retrieve.mockRejectedValue(new Error("Stripe API timeout"));

      const { createProKey } = await import("../services/keys.js");
      
      // Send webhook request
      const res = await request(app)
        .post("/v1/billing/webhook")
        .set("content-type", "application/json")
        .set("stripe-signature", "valid_sig")
        .send(JSON.stringify({ type: "checkout.session.completed" }));

      // Should return 200 but not provision key (graceful degradation)
      expect(res.status).toBe(200);
      expect(res.body.received).toBe(true);
      expect(createProKey).not.toHaveBeenCalled();
    });
  });

  describe("Line 165: /success route - !customerId check", () => {
    it("RED: should return 400 when customerId is missing", async () => {
      // Mock: session has no customer
      mockStripe.checkout.sessions.retrieve.mockResolvedValue({
        id: "cs_no_customer",
        customer: null,
        customer_details: { email: "test@test.com" },
      });

      const res = await request(app).get("/v1/billing/success?session_id=cs_no_customer");
      
      expect(res.status).toBe(400);
      expect(res.body.error).toMatch(/No customer found/);
    });

    it("RED: should return 400 when customerId is empty string", async () => {
      mockStripe.checkout.sessions.retrieve.mockResolvedValue({
        id: "cs_empty_customer",
        customer: "",
        customer_details: { email: "test@test.com" },
      });

      const res = await request(app).get("/v1/billing/success?session_id=cs_empty_customer");
      
      expect(res.status).toBe(400);
      expect(res.body.error).toMatch(/No customer found/);
    });
  });

  describe("Line 315: getOrCreateProPrice() - else branch (no existing product)", () => {
    it("RED: should create new product when products.search returns empty", async () => {
      // Mock: no existing product found
      mockStripe.products.search.mockResolvedValue({ data: [] });
      
      // Mock: product.create returns new product
      mockStripe.products.create.mockResolvedValue({ id: "prod_new_created" });
      
      // Mock: price.create returns new price
      mockStripe.prices.create.mockResolvedValue({ id: "price_new_created" });

      // Mock: checkout.sessions.create succeeds
      mockStripe.checkout.sessions.create.mockResolvedValue({ 
        id: "cs_new_product", 
        url: "https://checkout.stripe.com/pay/cs_new" 
      });

      const res = await request(app)
        .post("/v1/billing/checkout")
        .send({});

      expect(res.status).toBe(200);
      
      // Verify product was created
      expect(mockStripe.products.create).toHaveBeenCalledWith({
        name: "DocFast Pro",
        description: "5,000 PDFs / month via API. HTML, Markdown, and URL to PDF.",
      });
      
      // Verify price was created with the new product ID
      expect(mockStripe.prices.create).toHaveBeenCalledWith({
        product: "prod_new_created",
        unit_amount: 900,
        currency: "eur",
        recurring: { interval: "month" },
      });
      
      // Verify checkout session was created with the new price
      expect(mockStripe.checkout.sessions.create).toHaveBeenCalledWith(
        expect.objectContaining({
          line_items: [{ price: "price_new_created", quantity: 1 }],
        })
      );
    });
  });
});