allow empty values passed to Usernotes constructor

src/classes/Usernotes.test.ts

@@ -3,7 +3,19 @@ import {compressBlob, decompressBlob} from '../helpers/usernotes';
 import type {RawUsernotes} from '../types/RawUsernotes';
 import {Usernotes} from './Usernotes';
 
-test.todo('constructor');
+test('constructor: accept empty input', t => {
+	t.assert(
+		new Usernotes() instanceof Usernotes,
+		'passing nothing to Usernotes constructor should return a Usernotes instance',
+	);
+
+	t.assert(
+		new Usernotes('') instanceof Usernotes,
+		'passing empty string to Usernotes constructor should return a Usernotes instance',
+	);
+});
+
+test.todo('constructor: most other things');
 
 test.todo('get: most other things');
 

src/classes/Usernotes.ts

@@ -19,7 +19,12 @@ export class Usernotes {
 	/** A mapping of usernames to notes on the given user. */
 	private users = new Map<string, Usernote[]>();
 
-	constructor (jsonString: string) {
+	constructor (jsonString?: string) {
+		// if we have no data to start with, we start fresh
+		if (!jsonString) {
+			return;
+		}
+
 		let data = migrateUsernotesToLatestSchema(JSON.parse(jsonString));
 		const rawUsers = decompressBlob(data.blob);