How to mock $env/static/public with vitest?

I'm using an env variable MY_VAR that I use from $env/static/public

import { MY_VAR } from '$env/static/public';

export const myVar = MY_VAR === 'true';

I'd like to mock it in some tests, to support the 2 scenarios: MY_VAR build true / false. But I cannot manage to do it. I'm using vitest.

I tried setting up a mock file __mock__/env/static/public.ts with :

export const MY_VAR = 'false';

with vitest.config.ts:

export default defineConfig(({ mode }) => ({
    // ...
    resolve: {
        alias: {
            '$env/static/public': path.resolve(__dirname, '__mocks__/env/static/public')
        }
    }
}));

I also tried some combination of vi.mock, vi.hoisted, vi.spyOn but I couldn't manage to make it work.

How can I mock $env/static/public with vitest?

vi.mock() should work fine:

vi.mock('$env/static/public', () => {
  return Promise.resolve({
    MY_VAR: 'mock value'
  });
});

You put this at the top, although I think these mockings are always hoisted, so maybe the position doesn't matter.