Mock dependency in jest with typescript

Question

When testing a module that has a dependency in a different file. When assigning that module to be jest.Mock typescript gives an error that the method mock

Answer 1

Use the mocked helper from ts-jest like explained here

// foo.spec.ts
import { mocked } from 'ts-jest/utils'
import { foo } from './foo'
jest.mock('./foo')

// here the whole foo var is mocked deeply
const mockedFoo = mocked(foo, true)

test('deep', () => {
  // there will be no TS error here, and you'll have completion in modern IDEs
  mockedFoo.a.b.c.hello('me')
  // same here
  expect(mockedFoo.a.b.c.hello.mock.calls).toHaveLength(1)
})

test('direct', () => {
  foo.name()
  // here only foo.name is mocked (or its methods if it's an object)
  expect(mocked(foo.name).mock.calls).toHaveLength(1)
})

and if

• you use tslint
• ts-jest is in your dev-dependencies,

add this rule to your tslint.json: "no-implicit-dependencies": [true, "dev"]