How do I exclude files from svelte-kit build? - sveltekit

Question

If I run npm run build with SvelteKit it seems to include all files from the src folder. Is it possible to exclude a certain file type (eg. *test.js)?
Example
Select demo app with npm init svelte#next my-app
Add the following code to src/routes/todos/foo.test.js
describe('foo', () => {
it('temp', () => {
expect(true).toBe(false)
})
})
npm run build
npm run preview
Result: describe is not defined
Workaround
Move tests outside of src

Answer 1

UPDATE: SvelteKit 1.0.0-beta now requires pages/endpoints to follow a specific naming pattern, so explicit file exclusion should no longer be needed.
SvelteKit specially handles files in the routes/ directory with the following filenames (note the leading + in each filename):
+page.svelte
+page.js
+page.server.js
+error.js
+layout.svelte
+layout.js
+layout.server.js
+server.js
All other files are ignored and can be colocated in the routes/ directory.
If, for some reason, you need to have a file that has a special name shown above, it's currently not possible to exclude that file from special processing.
Original outdated answer:
SvelteKit 1.0.0-beta supports a routes configuration that enables file exclusion from the src/routes directory. The config value is a function that receives a file path as an argument, and returns true to use the file as a route.
For example, the following routes config excludes *.test.js files from routes:
// sveltekit.config.js
⋮
const config = {
kit: {
⋮
routes: filepath => {
return ![
// exclude *test.js files
/\.test\.js$/,
// original default config
/(?:(?:^_|\/_)|(?:^\.|\/\.)(?!well-known))/,
].some(regex => regex.test(filepath))
},
},
}
demo