Feat/frontend vitest (#6469)

* Added vitest tests.

* Added Settings tests to vitest - not working

* Added attributes and attributemap to vitest.

* Added more tests.

* Also run the vitest tests.

* Also run withoutPlugins

* Fixed pnpm lock

src/tests/backend-new/specs/skiplist.ts

@@ -0,0 +1,55 @@
+'use strict';
+
+const SkipList = require('ep_etherpad-lite/static/js/skiplist');
+import {expect, describe, it} from 'vitest';
+
+describe('skiplist.js', function () {
+  it('rejects null keys', async function () {
+    const skiplist = new SkipList();
+    for (const key of [undefined, null]) {
+      expect(() => skiplist.push({key})).toThrowError();
+    }
+  });
+
+  it('rejects duplicate keys', async function () {
+    const skiplist = new SkipList();
+    skiplist.push({key: 'foo'});
+    expect(() => skiplist.push({key: 'foo'})).toThrowError();
+  });
+
+  it('atOffset() returns last entry that touches offset', async function () {
+    const skiplist = new SkipList();
+    const entries: { key: string; width: number; }[] = [];
+    let nextId = 0;
+    const makeEntry = (width: number) => {
+      const entry = {key: `id${nextId++}`, width};
+      entries.push(entry);
+      return entry;
+    };
+
+    skiplist.push(makeEntry(5));
+    expect(skiplist.atOffset(4)).toBe(entries[0]);
+    expect(skiplist.atOffset(5)).toBe(entries[0]);
+    expect(() => skiplist.atOffset(6)).toThrowError();
+
+    skiplist.push(makeEntry(0));
+    expect(skiplist.atOffset(4)).toBe(entries[0]);
+    expect(skiplist.atOffset(5)).toBe(entries[1]);
+    expect(() => skiplist.atOffset(6)).toThrowError();
+
+    skiplist.push(makeEntry(0));
+    expect(skiplist.atOffset(4)).toBe(entries[0]);
+    expect(skiplist.atOffset(5)).toBe(entries[2]);
+    expect(() => skiplist.atOffset(6)).toThrowError();
+
+    skiplist.splice(2, 0, [makeEntry(0)]);
+    expect(skiplist.atOffset(4)).toBe(entries[0]);
+    expect(skiplist.atOffset(5)).toBe(entries[2]);
+    expect(() => skiplist.atOffset(6)).toThrowError();
+
+    skiplist.push(makeEntry(3));
+    expect(skiplist.atOffset(4)).toBe(entries[0]);
+    expect(skiplist.atOffset(5)).toBe(entries[4]);
+    expect(skiplist.atOffset(6)).toBe(entries[4]);
+  });
+});