js: tests/unit: Add test for Postbox labels

Should vanish when `require-author`/email is set in config.

isso/js/tests/unit/postbox-labels-optional.test.js

@@ -0,0 +1,48 @@
+/**
+ * @jest-environment jsdom
+ */
+
+/* Keep the above exactly as-is!
+ * https://jestjs.io/docs/configuration#testenvironment-string
+ * https://jestjs.io/docs/configuration#testenvironmentoptions-object
+ */
+
+"use strict";
+
+test('"(optional)" labels in Postox vanish if require-author/-email set', () => {
+  // Set up our document body
+  document.body.innerHTML =
+    '<div id=isso-thread></div>' +
+    '<script src="http://isso.api/js/embed.min.js"'
+          + 'data-isso="/"'
+          + 'data-isso-lang="de"' // falls back to "en" for placeholders
+          + '></script>';
+
+  const isso = require("app/isso");
+  const $ = require("app/dom");
+
+  var config = require("app/config");
+  config['require-author'] = true;
+  config['require-email'] = true;
+
+  const i18n = require("app/i18n");
+  const svg = require("app/svg");
+
+  const template = require("app/template");
+
+  template.set("conf", config);
+  template.set("i18n", i18n.translate);
+  template.set("pluralize", i18n.pluralize);
+  template.set("svg", svg);
+
+  var isso_thread = $('#isso-thread');
+  isso_thread.append('<div id="isso-root"></div>');
+  isso_thread.append(new isso.Postbox(null));
+
+  expect($("#isso-postbox-author").placeholder).toBe('John Doe');
+  expect($("#isso-postbox-email").placeholder).toBe('[email protected]');
+  // Instead of "Name (optional)"
+  expect($("[for='isso-postbox-author']").textContent).toBe('Name');
+  // Instead of "E-mail (optional)"
+  expect($("[for='isso-postbox-email']").textContent).toBe('E-Mail');
+});