How To Mock A Function That Returns A Value
In this article we are demostrate how to mock a function that returns a value.
Procedure
- Create the react app
npc create-react-app demo-mocking-return-value
. - Change directory
cd demo-mocking-return-value
-
Create the file
DemoMockReturnValue.js
in thesrc
directory. A referance to the function f is passed to the component as a prop. The function f is called and the result from the function is used to update the div with the test id myresult.
DemoMockReturnValue.js -
Create the file
DemoMockReturnValue.test.js
in thesrc
directory. The unit test will create a mocked function f using the jest libraryconst f = jest.fn();
. The function is confirmed to return a value using the codef.mockReturnValue(expectedValue);
. The assert confirms that the div with the test id myresult contains the expected data.
DemoMockReturnValue.test.js - Run the tests
npm test