use getBy query instead of queryBy when asserting for elements present in document (#2951)

* replace queryByText with getByText when asserting for presence of element

* use string instead of regex for line numbers

* cleanup test case of CodeSnippet

.changeset/lovely-suits-flash.md

@@ -0,0 +1,5 @@
+---
+'@backstage/core': patch
+---
+
+update the test cases of CodeSnippet component

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

@@ -20,10 +20,10 @@ import { wrapInTestApp } from '@backstage/test-utils';
 
 import { CodeSnippet } from './CodeSnippet';
 
-const JAVASCRIPT = `const greeting = "Hello";
-const world = "World";
-
-const greet = person => gretting + " " + person + "!";
+const JAVASCRIPT = `
+  const greeting = "Hello";
+  const world = "World";
+  const greet = person => gretting + " " + person + "!";
 `;
 
 const minProps = {
@@ -48,20 +48,20 @@ describe('<CodeSnippet />', () => {
   });
 
   it('renders with line numbers', () => {
-    const { queryByText } = render(
+    const { getByText } = render(
       wrapInTestApp(<CodeSnippet {...minProps} showLineNumbers />),
     );
-    expect(queryByText(/1/)).toBeInTheDocument();
-    expect(queryByText(/2/)).toBeInTheDocument();
-    expect(queryByText(/3/)).toBeInTheDocument();
+    expect(getByText('1')).toBeInTheDocument();
+    expect(getByText('2')).toBeInTheDocument();
+    expect(getByText('3')).toBeInTheDocument();
   });
 
   it('copy code using button', async () => {
     document.execCommand = jest.fn();
-    const rendered = render(
+    const { getByTitle } = render(
       wrapInTestApp(<CodeSnippet {...minProps} showCopyCodeButton />),
     );
-    const button = rendered.getByTitle('Text copied to clipboard');
+    const button = getByTitle('Text copied to clipboard');
     fireEvent.click(button);
     expect(document.execCommand).toHaveBeenCalled();
   });