October 18, 2023 - vi.mock('@store/actionCreators...gOrdersViewsBanner', () => { // ... }); In other words, your calls to vi.mock are not running inside the it functions....

April 8, 2026 - import * as exports from './example.js' vi.spyOn(exports, 'getter', 'get').mockReturnValue('mocked') WARNING · This will not work in the Browser Mode. For a workaround, see Limitations. Example with vi.mock: WARNING · Don't forget that a vi.mock call is hoisted to top of the file. It will always be executed before all imports. example.js · ts · export function method() {} ts ·

March 21, 2026 - The custom function implementation in the types below is marked with a generic <T>. ... Shorthand methods like mockReturnValue, mockReturnValueOnce, mockResolvedValue and others cannot be used on a mocked class.

vi.mock('../../../contexts/EntityContext'); vi.mock('../../../hooks/useAuth'); import { useEntityContext } from '../../../contexts/EntityContext'; import { useAuth0 } from '../../../hooks/useAuth'; describe('AccountSelection', () => { const mockUseEntityContext = vi.mocked(useEntityContext); const mockUseAuth0 = vi.mocked(useAuth0); const mockEntityContext = createMockEntityContext({ currentEntity: createMockEntity({ id: 'entity-123', // Keep predictable for URL matching in tests }), isSwitchingEntity: false, organizationId: 'org-123', // Keep predictable for tests }); beforeEach(() => { vi.cl

March 8, 2024 - // test.test.ts - this also passes but then barFn is not a mock so i cannot change its // implementation per test import { barFn } from './bar'; import { fooFn } from './foo'; vi.mock('./bar', () => ({ barFn: () => ({ bar: 3 }), })); describe.only('test', () => { // PASSES it('should return mocked bar', () => { const actual = fooFn(); expect(actual).toBe(3); }); // FAILS - barFn is not a mock it('should also return mocked bar', () => { // TypeError: barFn.mockReturnValue is not a function barFn.mockReturnValue({ bar: 4 }); const actual = fooFn(); expect(actual).toBe(4); }); }); Mac M1 Sonoma 14.3 Vitest: ├─ @vitest/coverage-v8@0.34.6 ├─ @vitest/expect@1.2.2 ├─ @vitest/runner@1.2.2 ├─ @vitest/snapshot@1.2.2 ├─ @vitest/spy@1.2.2 ├─ @vitest/utils@1.2.2 └─ vitest@1.2.2 typescript@5.3.2 ·

February 1, 2024 - import mockFsExtra from 'fs-extra'; import { describe, test, expect, vi } from 'vitest'; import * as a from './a.js'; vi.mock('fs-extra', async () => { const fsExtra = await vi.importActual('fs-extra'); return { ...fsExtra, pathExistsSync: vi.fn(), }; }); describe('a', () => { test('does path exist', () => { mockFsExtra.pathExistsSync.mockReturnValue(false); expect(a.doesPathExist()).toBe(false); }); }); Yet the test fails with the error TypeError: default.pathExistsSync.mockReturnValue is not a function.

June 21, 2024 - default.dispatch should give you a hint that the dispatch function should be defined on default: https://vitest.dev/guide/migration.html#module-mocks

October 2, 2025 - I want to use mockReturnValue() on a module that has been vi.mock()ed, but I can't mock the function implementation. // main_a.ts if (import.meta.vitest) { const { describe, it, expect, vi } = import.meta.vitest; vi.mock('./x.ts', () => ({ getName: vi.fn(() => '[[mocked from a]]'), })); describe('run', () => { it('enable mock', () => { vi.mocked(getName).mockReturnValue('[[mocked in test]]'); const res = run(); // If mocking is enabled, `[[mocked in test]]` should be returned.

Please reload this page. Something went wrong. There was an error while loading. Please reload this page. ... There is no API in Vitest that will allow you to partially pass data to a mocked function.

July 11, 2023 - This is an array containing all instances that were instantiated when mock was called with a new keyword. Note, this is an actual context (this) of the function, not a return value.

Checks that a given parameter is a mock function.

November 12, 2024 - Accepts a value that will be returned whenever the mock function is called. TypeScript will only accept values that match the return type of the original function. When the mocked function runs out of implementations, it will invoke the default ...

October 16, 2022 - If, in the factory function, I use vi.fn implementation, mockReturnValue or mockImplementation, instead of the desired value I obtain undefined. I've reproduced all three cases on stackblitz, using 0.24.3 version: you can find the in the mock.test.ts file. https://stackblitz.com/edit/vitest-dev-vitest-nccs1u?file=test/mock-with-implementation.test.ts ·

When you mock a module, Vitest will replace every exported function with a mock definition that, by default, does nothing and returns undefined.

April 14, 2026 - The simplest way to create a mock is with vi.fn(). This gives you a function that does nothing by default (returns undefined), but tracks every call made to it:

Vitest allows chaining multiple mock methods for complex scenarios: ... const complexMock = vi.fn() .mockReturnValueOnce(true) .mockImplementationOnce(() => { throw new Error('Custom error'); }) .mockReturnValue(false); test('complex mock behavior', () => { expect(complexMock()).toBe(true); expect(() => complexMock()).toThrow('Custom error'); expect(complexMock()).toBe(false); });

April 6, 2026 - import { mockDeep } from 'vitest-mock-extended'; const mockObj: DeepMockProxy<Test1> = mockDeep<Test1>({ funcPropSupport: true }); mockObj.deepProp.calledWith(1).mockReturnValue(3); mockObj.deepProp.getNumber.calledWith(1).mockReturnValue(4); expect(mockObj.deepProp(1)).toBe(3); expect(mockObj.deepProp.getNumber(1)).toBe(4); You can also provide a fallback mock implementation to be used if you do not define a return value using calledWith.