Node.js TypeScript环境下使用Jest模拟Stripe API遇到的问题

Let's break down why your current approaches aren't working and fix them step by step. The core issue here is that your stripe.ts module exports a pre-initialized Stripe instance, not the Stripe constructor function. Your mock setups weren't matching this export structure, leading to the undefined error.

Why Your Original Methods Failed #

1. Method 1 (mocks directory): You mocked the Stripe constructor, but your business code imports the already-created instance from stripe.ts, not the constructor itself. Modifying Stripe.prototype had no effect on the instance your code was actually using.
2. Method 2 (Direct test mock): You returned a function from your mock instead of an object matching the Stripe instance structure. Your code tried to access stripe.customers on a function, which doesn't have that property—hence the undefined error.

Solution 1: Use a mocks Directory Correctly #

Since your module exports an instance, your mock should export a matching mock instance.

Step 1: Create the Mock File #

Create src/payment-gateways/__mocks__/stripe.ts (note the directory placement: it should sit alongside the real stripe.ts, not in your tests folder):

// src/payment-gateways/__mocks__/stripe.ts
const mockCustomerCreate = jest.fn(() => Promise.resolve({ id: 'test-customer-123' }));

export default {
  customers: {
    create: mockCustomerCreate
  }
};

Step 2: Use the Mock in Your Test #

In stripe.test.ts, tell Jest to use your mock and assert against it:

// src/tests/stripe.test.ts
import stripe from '../../payment-gateways/stripe';

// Enable the mock for the stripe module
jest.mock('../../payment-gateways/stripe');

describe('stripe workflow', () => {
  beforeEach(() => {
    // Reset mock calls between tests to avoid cross-test pollution
    jest.clearAllMocks();
  });

  it('creates a customer', async () => {
    // Execute your business logic (e.g., Apollo mutation)
    await apollo.mutate({ /* your mutation details */ });

    // Assert the create method was called
    expect(stripe.customers.create).toHaveBeenCalled();
    // Optional: Assert with specific expected parameters
    expect(stripe.customers.create).toHaveBeenCalledWith({
      email: 'test@example.com',
      // Add other expected fields here
    });
  });
});

Solution 2: Direct Mock in the Test File #

If you prefer not to use a mocks directory, adjust your direct mock to return an object matching the Stripe instance structure (not a function):

// src/tests/stripe.test.ts
// Mock the stripe module directly, returning a mock instance
jest.mock('../../payment-gateways/stripe', () => ({
  customers: {
    create: jest.fn(() => Promise.resolve({ id: 'test-customer-123' }))
  }
}));

import stripe from '../../payment-gateways/stripe';

describe('stripe workflow', () => {
  beforeEach(() => {
    jest.clearAllMocks();
  });

  it('creates a customer', async () => {
    await apollo.mutate({ /* your mutation details */ });

    expect(stripe.customers.create).toHaveBeenCalled();
  });
});

Key Takeaways #

• Always match your mock structure to what your module actually exports. Since stripe.ts exports an instance, your mock must be an object with the same properties (like customers.create).
• Use jest.clearAllMocks() in beforeEach to reset mock state between tests, ensuring clean test runs.
• If you need to mock more Stripe methods later, just extend the mock object with additional properties (e.g., charges: { create: jest.fn() }).

内容的提问来源于stack exchange，提问作者PmmZenha