Andrew Seaford

In this article we are demostrate how to mock a function and confirm the function was called multiple times with two different tests of arguments.

Procedure

• Create the react app npc create-react-app demo-mocking-function-calls.
• Change directory cd demo-mocking-function-calls

• Create the file DemoMockingFunctionCalls.js in the src directory. A referance to the function f is passed as an argument to the function DemoMockingFunctionCalls. The function calls f twice with two different sets of arguments.
  DemoMockingFunctionCalls.js

• Create the file DemoMockingFunctionCalls.test.js in the src directory. The unit test will create a mocked function f using the jest library const f = jest.fn();. The assert checks that the function was called twice by checking the f.mock.calls matches the array of expected calls.
  DemoMockingFunctionCalls.test.js

• Run the tests npm test