(test): ensure error in node env w/ localStorage

- add node test to reach 100% code coverage!

- would prefer this test be in the same file as the others, but
  unfortunately jest only allows setting jest-environment on a per
  file basis, not on a per test or per test suite basis :/

test/index.node.spec.ts

@@ -0,0 +1,16 @@
+/**
+ * @jest-environment node
+ */
+// add tests in this file that are specific to node (vs. jsdom)
+
+/// <reference types="@types/jest" />
+
+import { persist } from '../src/index'
+import { UserStoreF } from './fixtures'
+
+describe('node usage', () => {
+  it('should error on default localStorage usage', async () => {
+    const user = UserStoreF.create()
+    await expect(persist('user', user)).rejects.toMatch(/^localStorage.+$/)
+  })
+})