Svelte

Svelte has no class-based dependency injection, so vitest-auto-spy/svelte adds no helper of its own — it is a recipe, not a framework integration. Svelte apps typically keep their logic in plain class-based services or stores; createSpyFromClass spies that class, and you inject the spy into the component under test (props, context, or a mocked module) exactly the way the component receives the real one.

import { createSpyFromClass } from 'vitest-auto-spy/svelte';
import { render } from '@testing-library/svelte';
import Cart from './Cart.svelte';
import { CartStore } from './cart-store';

const cartStore = createSpyFromClass(CartStore);
cartStore.total.mockReturnValue(42);

render(Cart, { props: { store: cartStore } });

Importing this entry registers the default Vitest mock adapter and re-exports the whole core, so a Svelte suite needs a single import. It pulls in neither svelte nor @testing-library/svelte.

Through context

When the component reads its collaborator from getContext, seed the same key with the spy:

import { render, screen } from '@testing-library/svelte';
import { expect, it } from 'vitest';
import { createSpyFromClass } from 'vitest-auto-spy/svelte';

import Cart from './Cart.svelte';
import { CART_STORE, CartStore } from './cart-store';

it('renders the total the store reports', () => {
  const cartStore = createSpyFromClass(CartStore);

  cartStore.total.mockReturnValue(42);

  render(Cart, { context: new Map([[CART_STORE, cartStore]]) });

  expect(screen.getByText('$42')).toBeInTheDocument();
});

Through a mocked module

When the component imports a singleton directly, replace the module — the spy is what the factory returns:

import { render } from '@testing-library/svelte';
import { expect, it, vi } from 'vitest';
import { createSpyFromClass } from 'vitest-auto-spy/svelte';

import { CartStore } from './cart-store';

const cartStore = vi.hoisted(() => createSpyFromClass(CartStore));

vi.mock('./cart-store', async (importOriginal) => ({
  ...(await importOriginal<typeof import('./cart-store')>()),
  cartStore,
}));

it('checks out through the module singleton', async () => {
  cartStore.checkout.resolveWith({ orderId: 'ord_42' });

  render(await import('./Cart.svelte').then((m) => m.default));

  expect(cartStore.checkout).toHaveBeenCalled();
});

vi.mock needs a module boundary

A vi.mock factory is hoisted above the file's own imports, so it must not close over anything declared at module scope — vi.hoisted is what makes the spy available to it. And in setups that bundle the spec (Angular's @angular/build:unit-test builder, for instance) a relative path has no module boundary left to replace; inject the spy through props or context there instead.