headplane/tests/unit/setup/overlay-fs.ts

import { vi } from 'vitest';

const fakeFs = new Map<string, string>();
export function createFakeFile(path: string, content: string) {
	fakeFs.set(path, content);
}

export function clearFakeFiles() {
	fakeFs.clear();
}

// @ts-expect-error: I have no clue why vitest's types are wrong here
vi.mock(import('node:fs/promises'), async (importOrig) => {
	const orig = await importOrig();
	return {
		...orig,
		readFile: (path, options) => {
			const p = path.toString();
			if (fakeFs.has(p)) {
				const content = fakeFs.get(p)!;
				if (typeof options === 'string' || options?.encoding) {
					return Promise.resolve(content);
				}

				return Promise.resolve(Buffer.from(content));
			}

			return orig.readFile.call(this, path, options);
		},

		access: (path, mode) => {
			const p = path.toString();
			if (fakeFs.has(p)) {
				return Promise.resolve();
			}

			return orig.access.call(this, path, mode);
		},
	};
});