Imported variable undefined inside Svelte component - jestjs

Question

This test:
import { render } from '#testing-library/svelte';
import { setRoutes } from '../router';
import SLink from '../router/components/SLink.svelte';
import routes from '../routes';
beforeAll(() => setRoutes(routes));
test('Instantiates components', () => {
expect(() => render(SLink, { props: { name: 'About' } })).not.toThrow();
});
Produces this error:
Error name: "TypeError"
Error message: "Cannot read property 'forEach' of undefined"
137 |
138 | const matchRoute = passedRoutes => {
> 139 | passedRoutes.forEach(compare => {
| ^
140 | if (matchedRoute) return;
141 |
142 | const { regex, fullRegex } = compare as FormattedRoute;
Which comes from this function:
const compareRoutes = (routes, route) => {
let matchedRoute;
const matchRoute = passedRoutes => {
passedRoutes.forEach(compare => {
// ...
});
};
matchRoute(routes);
return matchedRoute;
};
Which is called by the component I'm trying to render in the test:
<script>
import { routes } from '../logic';
import { compareRoutes } from '../static';
export let name;
// Error stems from 'routes' being undefined here
const route = compareRoutes(routes, { name });
</script>
This line:
beforeAll(() => setRoutes(routes));
Sets the routes imported by SLink which are then passed to compareRoutes, so they shouldn't be undefined.
I've used the same line for other functions and the tests run as expected.
Can #testing-library/svelte not resolve imports? Or, is there another reason for this?
setRoutes:
let routes;
const setRoutes = (userRoutes) => {
// ...
routes = userRoutes;
};
export { routes };

Answer 1

I guess this is rendered in JSDom, and I suspect it might not support live bindings like what you're doing with your export { routes }.
Try exporting a function instead, to confirm:
export const getRoutes = () => routes
Also, this is off topic, but it really feels like your compareRoutes function could be simplified as a filter (or map, or reduce) operation. Something like that:
const compareRoutes = (routes, route) => routes.filter(
x => route.path.startsWith(x.path)
)