fix CodeSnippet test case warnings

packages/core/src/components/CodeSnippet/CodeSnippet.test.tsx

@@ -15,8 +15,9 @@
  */
 
 import React from 'react';
-import { render, fireEvent } from '@testing-library/react';
-import { wrapInTestApp } from '@backstage/test-utils';
+import { fireEvent } from '@testing-library/react';
+import { act } from 'react-dom/test-utils';
+import { renderInTestApp } from '@backstage/test-utils';
 
 import { CodeSnippet } from './CodeSnippet';
 
@@ -32,24 +33,24 @@ const minProps = {
 };
 
 describe('<CodeSnippet />', () => {
-  it('renders text without exploding', () => {
-    const { getByText } = render(wrapInTestApp(<CodeSnippet {...minProps} />));
+  it('renders text without exploding', async () => {
+    const { getByText } = await renderInTestApp(<CodeSnippet {...minProps} />);
     expect(getByText(/"Hello"/)).toBeInTheDocument();
     expect(getByText(/"World"/)).toBeInTheDocument();
   });
 
-  it('renders without line numbers', () => {
-    const { queryByText } = render(
-      wrapInTestApp(<CodeSnippet {...minProps} />),
+  it('renders without line numbers', async () => {
+    const { queryByText } = await renderInTestApp(
+      <CodeSnippet {...minProps} />,
     );
     expect(queryByText('1')).not.toBeInTheDocument();
     expect(queryByText('2')).not.toBeInTheDocument();
     expect(queryByText('3')).not.toBeInTheDocument();
   });
 
-  it('renders with line numbers', () => {
-    const { getByText } = render(
-      wrapInTestApp(<CodeSnippet {...minProps} showLineNumbers />),
+  it('renders with line numbers', async () => {
+    const { getByText } = await renderInTestApp(
+      <CodeSnippet {...minProps} showLineNumbers />,
     );
     expect(getByText('1')).toBeInTheDocument();
     expect(getByText('2')).toBeInTheDocument();
@@ -57,12 +58,17 @@ describe('<CodeSnippet />', () => {
   });
 
   it('copy code using button', async () => {
+    jest.useFakeTimers();
     document.execCommand = jest.fn();
-    const { getByTitle } = render(
-      wrapInTestApp(<CodeSnippet {...minProps} showCopyCodeButton />),
+    const { getByTitle } = await renderInTestApp(
+      <CodeSnippet {...minProps} showCopyCodeButton />,
     );
     const button = getByTitle('Text copied to clipboard');
     fireEvent.click(button);
+    act(() => {
+      jest.runAllTimers();
+    });
     expect(document.execCommand).toHaveBeenCalled();
+    jest.useRealTimers();
   });
 });