diff --git a/packages/ui/components/core/test/SlotMixin.polyfill.test.js b/packages/ui/components/core/test/SlotMixin.polyfill.test.js
new file mode 100644
index 0000000000..5b9ebdd4f3
--- /dev/null
+++ b/packages/ui/components/core/test/SlotMixin.polyfill.test.js
@@ -0,0 +1,40 @@
+import sinon from 'sinon';
+import { defineCE, expect, fixture, 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';
+
+it('supports scoped elements when polyfill loaded', async () => {
+  // @ts-ignore the scoped-custom-element-registry polyfill makes sure `ShadowRoot.prototype.createElement` is defined
+  const createElementSpy = sinon.spy(ShadowRoot.prototype, 'createElement');
+
+  class ScopedEl extends LitElement {}
+
+  const tagName = defineCE(
+    class extends ScopedElementsMixin(SlotMixin(LitElement)) {
+      static get scopedElements() {
+        return {
+          // @ts-expect-error
+          ...super.scopedElements,
+          'scoped-elm': ScopedEl,
+        };
+      }
+
+      get slots() {
+        return {
+          ...super.slots,
+          template: () => html`<scoped-elm></scoped-elm>`,
+        };
+      }
+
+      render() {
+        return html`<slot name="template"></slot>`;
+      }
+    },
+  );
+
+  const tag = unsafeStatic(tagName);
+  await fixture(html`<${tag}></${tag}>`);
+
+  expect(createElementSpy.getCalls()).to.have.length(1);
+});
diff --git a/packages/ui/components/core/test/SlotMixin.test.js b/packages/ui/components/core/test/SlotMixin.test.js
index 413dbf77c9..e9b6dd57cc 100644
--- a/packages/ui/components/core/test/SlotMixin.test.js
+++ b/packages/ui/components/core/test/SlotMixin.test.js
@@ -1,6 +1,4 @@
-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';
 
@@ -8,24 +6,6 @@ import { LitElement } from 'lit';
  * @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(
@@ -566,86 +546,4 @@ describe('SlotMixin', () => {
       expect(el._templateNode.textContent).to.equal('1');
     });
   });
-
-  describe('Scoped Registries', () => {
-    it('supports scoped elements when polyfill loaded', async () => {
-      const outputObj = mockScopedRegistry();
-
-      class ScopedEl extends LitElement {}
-
-      const tagName = defineCE(
-        // @ts-ignore
-        class extends ScopedElementsMixin(SlotMixin(LitElement)) {
-          static get scopedElements() {
-            return {
-              // @ts-expect-error
-              ...super.scopedElements,
-              'scoped-elm': ScopedEl,
-            };
-          }
-
-          get slots() {
-            return {
-              ...super.slots,
-              template: () => html`<scoped-elm></scoped-elm>`,
-            };
-          }
-
-          render() {
-            return html`<slot name="template"></slot>`;
-          }
-        },
-      );
-
-      const tag = unsafeStatic(tagName);
-      await fixture(html`<${tag}></${tag}>`);
-
-      expect(outputObj.createElementCallCount).to.equal(1);
-
-      unMockScopedRegistry();
-    });
-
-    it('does not scope elements when polyfill not loaded', async () => {
-      // @ts-expect-error
-      ShadowRoot.prototype.createElement = null;
-      class ScopedEl extends LitElement {}
-
-      const tagName = defineCE(
-        class extends ScopedElementsMixin(SlotMixin(LitElement)) {
-          static get scopedElements() {
-            return {
-              // @ts-expect-error
-              ...super.scopedElements,
-              'scoped-el': ScopedEl,
-            };
-          }
-
-          get slots() {
-            return {
-              ...super.slots,
-              template: () => html`<scoped-el></scoped-el>`,
-            };
-          }
-
-          render() {
-            return html`<slot name="template"></slot>`;
-          }
-        },
-      );
-
-      const renderTarget = document.createElement('div');
-      const el = document.createElement(tagName);
-
-      // We don't use fixture, so we limit the amount of calls to document.createElement
-      const docSpy = sinon.spy(document, 'createElement');
-      document.body.appendChild(renderTarget);
-      renderTarget.appendChild(el);
-
-      expect(docSpy.callCount).to.equal(2);
-
-      document.body.removeChild(renderTarget);
-      docSpy.restore();
-      unMockScopedRegistry();
-    });
-  });
 });
diff --git a/web-test-runner.config.mjs b/web-test-runner.config.mjs
index 5f269c6da5..f89be72ae8 100644
--- a/web-test-runner.config.mjs
+++ b/web-test-runner.config.mjs
@@ -3,7 +3,7 @@ import { playwrightLauncher } from '@web/test-runner-playwright';
 
 const devMode = process.argv.includes('--dev-mode');
 
-const packages = fs
+const testGroups = fs
   .readdirSync('packages')
   .filter(
     dir => fs.statSync(`packages/${dir}`).isDirectory() && fs.existsSync(`packages/${dir}/test`),
@@ -18,21 +18,54 @@ const packages = fs
           fs.existsSync(`packages/ui/components/${dir}/test`),
       )
       .map(dir => ({ name: dir, path: `packages/ui/components/${dir}/test` })),
-  );
+  )
+  .map(pkg => ({
+    name: pkg.name,
+    files: `${pkg.path}/**/*.test.js`,
+  }));
 
-/**
- * @type {import('@web/test-runner').TestRunnerConfig['testRunnerHtml']}
- *
- */
-const testRunnerHtml = testRunnerImport =>
-  `
+const testsThatShouldRunWithScopedCustomElementRegistryPolyfill = testGroups.map(testGroup => {
+  const files = [
+    testGroup.files,
+    `!${testGroup.files.replace('*.test.js', '*.no-polyfill.test.js')}`,
+  ];
+  return {
+    name: testGroup.name,
+    files,
+    /**
+     * @type {import('@web/test-runner').TestRunnerConfig['testRunnerHtml']}
+     *
+     */
+    testRunnerHtml: testRunnerImport => `
 <html>
   <head>
     <script src="/node_modules/@webcomponents/scoped-custom-element-registry/scoped-custom-element-registry.min.js"></script>
     <script type="module" src="${testRunnerImport}"></script>
   </head>
 </html>
-`;
+`,
+  };
+});
+
+const testsThatShouldNotRunWithPolyfill = testGroups.map(testGroup => {
+  const files = [testGroup.files, `!${testGroup.files.replace('*.test.js', '*.polyfill.test.js')}`];
+
+  return {
+    name: testGroup.name,
+    files,
+    /**
+     * @type {import('@web/test-runner').TestRunnerConfig['testRunnerHtml']}
+     *
+     */
+    testRunnerHtml: testRunnerImport => `
+<html>
+  <head>
+    <script type="module" src="${testRunnerImport}"></script>
+  </head>
+</html>
+`,
+  };
+});
 
 export default {
   nodeResolve: { exportConditions: [devMode && 'development'] },
@@ -51,14 +84,13 @@ export default {
       timeout: '5000',
     },
   },
-  testRunnerHtml,
   browsers: [
     playwrightLauncher({ product: 'firefox', concurrency: 1 }),
     playwrightLauncher({ product: 'chromium' }),
     playwrightLauncher({ product: 'webkit' }),
   ],
-  groups: packages.map(pkg => ({
-    name: pkg.name,
-    files: `${pkg.path}/**/*.test.js`,
-  })),
+  groups: [].concat([
+    ...testsThatShouldRunWithScopedCustomElementRegistryPolyfill,
+    ...testsThatShouldNotRunWithPolyfill,
+  ]),
 };