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Authenticated Integration

Just like in higher level E2E tests, you often are required to simulate an authenticated user. This involves a few things:
  1. Inserting a test user in the database
  2. Creating a session for that user
  3. Setting the session ID in the cookie header for requests
  4. Handling Verification (like 2FA)
  5. Asserting the auth state is updated properly in responses
Depending on what you're testing, this may require a bit of work because you can't just set document.cookie and expect a new Request() to have the cookie value in there. The browser is the one that sets the request's cookie headers when an actual request is made. So if we create a request object in our test, the source code that checks request.headers.get('cookie') will just get null.
This means two things:
  1. If the request object is made by our source code, you won't be able to test it at this level (you'll have to use E2E)
  2. If the thing you're testing accepts a request object (or you can intercept it), you can set the cookie header yourself.

Loaders/Actions

In this case, we're the ones creating the Request object, so we can set this object ourselves and we already have in a previous exercise:
new Request(someUrl, {
	headers: { cookie: someCookieValue },
})
The trickiest bit here is that our application utilities are all about creating set-cookie headers for a response, not cookie headers for a request. But we've already used set-cookie-header parser to deal with this in playwright and it will be exactly the same in vitest with our integration tests as well.

Remix Stub

If you want to test your whole route, then you'll want to do something like this:
import { json, type DataFunctionArgs } from '@remix-run/node'
import { useLoaderData } from '@remix-run/react'

export async function loader({ request }: DataFunctionArgs) {
	const user = await getUser(request)
	return json({ title: `Hello ${user.name}` })
}
export default function HelloRoute() {
	const data = useLoaderData<typeof loader>()

	return <div>{data.title}</div>
}
import { createRemixStub } from '@remix-run/testing'
import { default as HelloRoute, loader } from './hello.tsx'

// ...

const App = createRemixStub([
	{
		path: '/hello',
		Component: HelloRoute,
		loader, // <-- pass the loader as-is
	},
])
But our loader in this example has this getUser utility which presumably looks up the user by the cookie in the request. Since Remix is responsible for creating this request, there's no way for us to set the cookie... Or is there? ๐Ÿ˜‰
const App = createRemixStub([
	{
		path: '/hello',
		Component: HelloRoute,
		loader: async args => {
			args.request.headers.set('cookie', 'my=cookie')
			return loader(args)
		},
	},
])
In this way we can still get full coverage of the loader, but we also get the opportunity to customize the data sent into the loader to simulate the logged in state. A win-win.