Sometimes, we want to change the behavior of a mocked import with Jest and JavaScript.
In this article, we’ll look at how to change the behavior of a mocked import with Jest and JavaScript.
How to change the behavior of a mocked import with Jest and JavaScript?
To change the behavior of a mocked import with Jest and JavaScript, we call the jest.mock
method.
For instance, we write
import { methodToMock } from "the-package-to-mock";
jest.mock("the-package-to-mock", () => ({
methodToMock: jest.fn(),
}));
it("test1", () => {
methodToMock.mockImplementation(() => "someValue");
});
it("test2", () => {
methodToMock.mockImplementation(() => "anotherValue");
});
to call jest.mock
to mock the methodToMock
method in the the-package-to-mock
module.
We set methodToMock
to the mock function returned by jest.fn
.
Then in our tests, we call methodToMock.mockImplementation
with a callback mocks the behavior of methodToMock
.
Conclusion
To change the behavior of a mocked import with Jest and JavaScript, we call the jest.mock
method.