test: define tutorial focus trap for #57

tests/tutorial-focus-trap.test.cjs

@@ -0,0 +1,63 @@
+const test = require('node:test');
+const assert = require('node:assert/strict');
+
+function createButton(id) {
+  return {
+    id,
+    disabled: false,
+    hidden: false,
+    offsetParent: {},
+    focusCalled: 0,
+    focus() { this.focusCalled += 1; },
+  };
+}
+
+test('tutorial focus trap wraps Tab from last button to first', () => {
+  const skip = createButton('tutorial-skip-btn');
+  const next = createButton('tutorial-next-btn');
+  const overlay = {
+    querySelectorAll() {
+      return [skip, next];
+    },
+  };
+  global.document = {
+    activeElement: next,
+    getElementById(id) {
+      return id === 'tutorial-overlay' ? overlay : null;
+    },
+    addEventListener() {},
+  };
+
+  const { trapTutorialFocus } = require('../js/tutorial.js');
+  let prevented = false;
+  const handled = trapTutorialFocus({ key: 'Tab', shiftKey: false, preventDefault() { prevented = true; } }, global.document);
+
+  assert.equal(handled, true);
+  assert.equal(prevented, true);
+  assert.equal(skip.focusCalled, 1);
+});
+
+test('tutorial focus trap wraps Shift+Tab from first button to last', () => {
+  const skip = createButton('tutorial-skip-btn');
+  const next = createButton('tutorial-next-btn');
+  const overlay = {
+    querySelectorAll() {
+      return [skip, next];
+    },
+  };
+  global.document = {
+    activeElement: skip,
+    getElementById(id) {
+      return id === 'tutorial-overlay' ? overlay : null;
+    },
+    addEventListener() {},
+  };
+
+  const { trapTutorialFocus } = require('../js/tutorial.js');
+  let prevented = false;
+  const handled = trapTutorialFocus({ key: 'Tab', shiftKey: true, preventDefault() { prevented = true; } }, global.document);
+
+  assert.equal(handled, true);
+  assert.equal(prevented, true);
+  assert.equal(next.focusCalled, 1);
+});