diff --git a/packages/ui/components/core/test/SlotMixin.test.js b/packages/ui/components/core/test/SlotMixin.test.js
index 413dbf77c..21b1f0c2a 100644
--- a/packages/ui/components/core/test/SlotMixin.test.js
+++ b/packages/ui/components/core/test/SlotMixin.test.js
@@ -1,31 +1,14 @@
-import sinon from 'sinon';
 import { defineCE, expect, fixture, fixtureSync, unsafeStatic, html } from '@open-wc/testing';
-import { ScopedElementsMixin } from '@open-wc/scoped-elements/lit-element.js';
 import { SlotMixin } from '@lion/ui/core.js';
 import { LitElement } from 'lit';
+import sinon from 'sinon';
+
+import { ScopedElementsMixin, supportsScopedRegistry } from '../src/ScopedElementsMixin.js';
 
 /**
  * @typedef {import('../types/SlotMixinTypes.js').SlotHost} SlotHost
  */
 
-// @ts-ignore
-const createElementNative = ShadowRoot.prototype.createElement;
-function mockScopedRegistry() {
-  const outputObj = { createElementCallCount: 0 };
-  // @ts-expect-error wait for browser support
-  ShadowRoot.prototype.createElement = (tagName, options) => {
-    outputObj.createElementCallCount += 1;
-    // Return an element that lit can use as render target
-    return createElementNative(tagName, options);
-  };
-  return outputObj;
-}
-
-function unMockScopedRegistry() {
-  // @ts-expect-error wait for browser support
-  ShadowRoot.prototype.createElement = createElementNative;
-}
-
 describe('SlotMixin', () => {
   it('inserts provided element into light dom and sets slot', async () => {
     const tag = defineCE(
@@ -568,8 +551,11 @@ describe('SlotMixin', () => {
   });
 
   describe('Scoped Registries', () => {
-    it('supports scoped elements when polyfill loaded', async () => {
-      const outputObj = mockScopedRegistry();
+    it('supports scoped elements when scoped registries supported (or polyfill loaded)', async () => {
+      if (!supportsScopedRegistry()) return;
+
+      // @ts-expect-error
+      const createElSpy = sinon.spy(ShadowRoot.prototype, 'createElement');
 
       class ScopedEl extends LitElement {}
 
@@ -600,14 +586,14 @@ describe('SlotMixin', () => {
       const tag = unsafeStatic(tagName);
       await fixture(html`<${tag}></${tag}>`);
 
-      expect(outputObj.createElementCallCount).to.equal(1);
+      expect(createElSpy.callCount).to.equal(1);
 
-      unMockScopedRegistry();
+      createElSpy.restore();
     });
 
-    it('does not scope elements when polyfill not loaded', async () => {
-      // @ts-expect-error
-      ShadowRoot.prototype.createElement = null;
+    it('does not scope elements when scoped registries not supported (or polyfill not loaded)', async () => {
+      if (supportsScopedRegistry()) return;
+
       class ScopedEl extends LitElement {}
 
       const tagName = defineCE(
@@ -645,7 +631,6 @@ describe('SlotMixin', () => {
 
       document.body.removeChild(renderTarget);
       docSpy.restore();
-      unMockScopedRegistry();
     });
   });
 });
diff --git a/packages/ui/components/form-core/test-suites/ValidateMixin.suite.js b/packages/ui/components/form-core/test-suites/ValidateMixin.suite.js
index f89d4fd3a..517b3822c 100644
--- a/packages/ui/components/form-core/test-suites/ValidateMixin.suite.js
+++ b/packages/ui/components/form-core/test-suites/ValidateMixin.suite.js
@@ -2,25 +2,25 @@ import { LitElement } from 'lit';
 import { aTimeout, defineCE, expect, fixture, html, unsafeStatic } from '@open-wc/testing';
 import {
   getFormControlMembers,
-  AlwaysInvalid,
-  AlwaysValid,
   AsyncAlwaysInvalid,
   AsyncAlwaysValid,
+  AlwaysInvalid,
+  AlwaysValid,
 } from '@lion/ui/form-core-test-helpers.js';
 import sinon from 'sinon';
 import {
+  ResultValidator,
+  ValidateMixin,
   EqualsLength,
+  Unparseable,
   MaxLength,
   MinLength,
-  Required,
-  ResultValidator,
-  Unparseable,
-  ValidateMixin,
   Validator,
+  Required,
 } from '@lion/ui/form-core.js';
 
-import '@lion/ui/define/lion-field.js';
 import '@lion/ui/define/lion-validation-feedback.js';
+import '@lion/ui/define/lion-field.js';
 
 /**
  * @typedef {import('@lion/ui/form-core.js').LionField} LionField