Jest 'spyOn' and typeScript

If you been coding with typescript and want to use 'spyOn' on your test you would have to type it like this.

let functionSpy: jest.SpyInstance;

This way we are telling the that it will be a spy instance and we will not have a ts problem.

Now, we are going to see how to actually use it which is really simple.

functionTest.tsx

const FunctionTest = () => {
  const bar = () => {
  return 'test'
}
 return(
  <div></div>
)
}

export default FunctionTest

functionTest.test.tsx

functionSpy = jest.spyOn(FunctionTest, 'bar');

Here we can see that following this simple step we are able to spy on the function in order to call it

Hope someone found it useFul.

Lautaro.