Use vitest for some EW unit tests (#33816)

* Use vitest for some EW unit tests

* Ensure library builds are done before unit tests

* Stabilise jest tests

* Move more tests over

* Make sonar happier

* Update types/node for happy-dom compat again

* Decrease max-workers to stabilise jest tests

* Split jest over 3 runners to alleviate memory woes

* Switch jest to runInBand

* Attempt to deflake jest tests

* tweak coverage

* tweak coverage

apps/web/src/utils/keepIfSame.test.ts

@@ -0,0 +1,24 @@
+/*
+ * Copyright 2026 Element Creations Ltd.
+ *
+ * SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only OR LicenseRef-Element-Commercial
+ * Please see LICENSE files in the repository root for full details.
+ */
+
+import { describe, it, expect } from "vitest";
+
+import { keepIfSame } from "./keepIfSame";
+
+describe("keepIfSame", () => {
+    it("returns the next value if the current and next values are not deeply equal", () => {
+        const current = { a: 1 };
+        const next = { a: 2 };
+        expect(keepIfSame(current, next)).toBe(next);
+    });
+
+    it("returns the current value if the current and next values are deeply equal", () => {
+        const current = { a: 1 };
+        const next = { a: 1 };
+        expect(keepIfSame(current, next)).toBe(current);
+    });
+});