mock console.log

test.js

// @flow
const sum = (a, b) => a + b

test('sum', () => {
  expect(sum(1, 2)).toBe(3)
})

const spyLog = jest.spyOn(console, 'log')
spyLog.mockImplementation(x => x)

const printSum = (a, b) => {
  console.log(`sum = ${sum(a, b)}`)
}

test('printSum', () => {
  printSum(1, 2)
  expect(console.log).toBeCalled()
  expect(spyLog.mock.calls[0][0]).toBe('sum = 3')
  spyLog.mockReset()
  spyLog.mockRestore()
})