I have the following health check function
export default function handler(req, res) {
res.status(200).json({ message: "Hello from Next.js!" });
}
and I have the following test
import handler from "./healthcheck"
describe("Healthcheck", () => {
test("that the application is live with a status of 200", () => {
const mockFn = jest.fn({
status: jest.fn(),
json: jest.fn()
});
expect(mockFn).toHaveBeenCalledWith();
expect(mockFn.status).toBe(200);
});
});
I want to check that the function is being called and that the status is 200, I know I need to mock out the function, however, how do I correctly mock out functions like this with a request and response.
The handler function accepts a res parameter that you can mock and pass to the handler call during the test. You can then verify the mocks have been properly called.
import handler from "./healthcheck"
describe("Healthcheck", () => {
test("that the application is live with a status of 200", () => {
const resMock = { status: jest.fn() }; // Mocks `res`
const resStatusMock = { json: jest.fn() }; // Mock `res.status`
resMock.status.mockReturnValue(resStatusMock); // Makes `res.status` return `resStatusMock`
handler(undefined, resMock);
expect(resMock.status).toHaveBeenCalledWith(200);
expect(resStatusMock.json).toHaveBeenCalledWith({
message: "Hello from Next.js!"
});
});
});