Mocking RN Linking

ExternalLink.test.js

import React from "react"
import { Linking } from "react-native"
import { cleanup, fireEvent } from "react-native-testing-library"

import { renderWithTheme } from "testHelpers/componentWrappers"

import ExternalLink from "./"

const externalLinkTestId = "external-link"

jest.mock("react-native/Libraries/Linking/Linking", () => ({
	openURL: jest.fn(() => Promise.resolve("mockResolve")),
}))

describe("[External Link]", () => {
	let componentRender

	beforeEach(() => {
		componentRender = () => renderWithTheme(
			<ExternalLink
				testID={externalLinkTestId}
				uri="mockURI"
			>
				test link
			</ExternalLink>
		)
	})

	afterEach(cleanup)

	it("displays the external link", () => {
		const { queryByTestId } = componentRender()
		expect(queryByTestId(externalLinkTestId)).not.toBeNull()
	})
	it("handles onPress as expected", () => {
		const { queryByTestId } = componentRender()
		fireEvent.press(queryByTestId(externalLinkTestId))
		expect(Linking.openURL).toHaveBeenCalledTimes(1)
	})
	it("logs promise catch error", () => {
		Linking.openURL = jest.fn(() => Promise.reject("mockError"))
		const { queryByTestId } = componentRender()
		fireEvent.press(queryByTestId(externalLinkTestId))
		expect(Linking.openURL).toHaveBeenCalledTimes(1)
	})
	it("handles disabled styles", () => {
		componentRender = () => renderWithTheme(
			<ExternalLink
				disabled
				testID={externalLinkTestId}
				uri="mockURI"
			>
				test link
			</ExternalLink>
		)
		const { queryByTestId } = componentRender()
		expect(queryByTestId(externalLinkTestId)).not.toBeNull()
	})
})

Can you explain line 12 to me?

@anabeatrizzz the second parameter for jest.mock is a module factory that returns back the mocked methods of the module, for this instance we are returning back a mocked implementation for the openURL method that Linking exports. If you don't mock the module and attempt to do any sort of verification of the module being called you will receive an error from jest due to the function not being a mocked one. Does that help?

Good method, but I have to also mock event listener functions to make it work.

jest.mock('react-native/Libraries/Linking/Linking', () => ({
  openURL: jest.fn().mockResolvedValue(null),
  addEventListener: jest.fn(),
  removeEventListener: jest.fn(),
}));

needed an example of mocking openURL in a pinch and this did the trick. Thank you!

@Coffeegerm yes, thanks!