Add basic JS tests

web/src/test/setup.js

@@ -0,0 +1,19 @@
+/* eslint-env node, es2021 */
+// Minimal window stub so the pure-logic modules import cleanly under the node environment,
+// without pulling in jsdom. utils.js -> config.js does `const { config } = window;` at import
+// time, and config.js falls back to window.location.origin when base_url is empty.
+globalThis.window = {
+  location: { origin: "https://ntfy.sh" },
+  config: { base_url: "", disallowed_topics: ["app", "account", "settings"] },
+  atob: globalThis.atob, // urlB64ToUint8Array uses window.atob; Node provides global atob
+};
+
+// utils.js -> Prefs.js -> db.js -> Session.username() reads localStorage at module load.
+// Node has no localStorage; an in-memory stand-in is enough for the pure-logic tests.
+const store = new Map();
+globalThis.localStorage = {
+  getItem: (key) => (store.has(key) ? store.get(key) : null),
+  setItem: (key, value) => store.set(key, String(value)),
+  removeItem: (key) => store.delete(key),
+  clear: () => store.clear(),
+};