Memory-router tests

Test route matching, navigation, middleware, and subscriptions with createMemoryRouter().

Use createMemoryRouter() when a test needs router state without a browser history implementation.

Memory-router tests should assert router behavior directly: current location, match ID, params, navigation state, errors, and subscriber calls.

Start at a route

import {
  createMemoryRouter,
  defineRoutes,
} from '@cookbook/router';

const routes = defineRoutes([
  {
    id: 'home',
    path: '/',
    view: 'home',
  },
  {
    id: 'users.details',
    path: '/users/{userId:int}',
    view: 'users.details',
  },
] as const);

const router = createMemoryRouter({
  routes,
  initialEntries: ['/users/42'],
});

await router.start();

expect(router.state.match?.id).toBe('users.details');
expect(router.state.match?.params).toEqual({
  userId: 42,
});

await router.navigate.to('users.details', {
  params: {
    userId: 7,
  },
});

expect(router.state.location.href).toBe('/users/7');
expect(router.state.match?.id).toBe('users.details');

Assert subscriptions

const states: string[] = [];

const unsubscribe = router.subscribe((state) => {
  states.push(state.location.href);
});

await router.navigate.to('/users/1');
await router.navigate.to('/users/2');

unsubscribe();

expect(states).toEqual([
  '/users/1',
  '/users/2',
]);

Subscribers receive state changes after visible router state changes.

Test middleware behavior

const router = createMemoryRouter({
  routes,
  initialEntries: ['/admin'],
  middleware: [
    (context) => {
      if (context.route.id === 'admin') {
        return context.redirect('/login');
      }
    },
  ],
});

await router.start();

expect(router.state.location.href).toBe('/login');

Clean up

router.dispose();

Disposal clears listeners, blockers, runtime middleware, subscribers, and preload state. It also prevents accidental reuse in later tests.

Where this bites

`router.state.match` can exist before `start()`

Initial state is created from the initial history location. start() still matters because it runs current-location transition work such as middleware, redirects, lifecycle, and error handling.

Memory history is not browser history

Memory history has no DOM events, scroll restoration, or external redirect transport. That is usually what core tests need.

Dispose routers in long-lived test processes

A disposed router cannot navigate again. Create a new router per test case.