setupLanguageModel function domain

function setupLanguageModel(
  availability: string,
  promptValue: string | Error = "test('improved', async () => {});",
) {
  const session = buildMockSession(promptValue);
  const create = vi.fn().mockResolvedValue(session);
  const availabilityFn = vi.fn().mockResolvedValue(availability);

  Reflect.set(globalThis as object, "LanguageModel", {
    availability: availabilityFn,
    create,
  });

  return { session, create, availabilityFn };
}