vitest/prefer-mock-return-shorthand

📝 Prefer mock return shorthands.

🔧 This rule is automatically fixable by the --fix CLI option.

When working with mocks of functions that return simple values, vitest provides some API sugar functions to reduce the amount of boilerplate you have to write.

These methods should be preferred when possible.

The following patterns are warnings

vi.fn().mockImplementation(() => 'hello world')

vi.spyOn(fs.promises, 'readFile').mockImplementationOnce(() =>
  Promise.reject(new Error('oh noes!')),
)

myFunction
  .mockImplementationOnce(() => 42)
  .mockImplementationOnce(() => Promise.resolve(42))
  .mockReturnValue(0)

The following patterns are not warnings

vi.fn().mockResolvedValue(123)

vi.spyOn(fs.promises, 'readFile').mockReturnValue(
  Promise.reject(new Error('oh noes!')),
)
vi.spyOn(fs.promises, 'readFile').mockRejectedValue(new Error('oh noes!'))

vi.spyOn(fs, 'readFileSync').mockImplementationOnce(() => {
  throw new Error('oh noes!')
})

myFunction
  .mockResolvedValueOnce(42)
  .mockResolvedValueOnce(42)
  .mockReturnValue(0)