As a Single Page Application (SPA) one of the primary features is the Next Router (next/router) which allows for integration between the navigation system (typically the browser's History API) and your application code to allow URL changes to control what component(s) are rendered.
The useRouter hook is a primary mechanism to integrate programmatic control of the Router into your components. It is relatively easy to mock out the hook function to return inspectable stub functions.
See stubbing out 'useRouter' hook in BackButton.cy.js
useRouter simply searches up the React stack to find a router provider - by building our own with a mocked router implementation we can inspect functions on the router itself for test assertions.
See use mock router implementation in BackButton.cy.js and the custom nextMount command in /cypress/support/component.js