add a lot more parseDOM tests to all extensions

docs/src/demos/Extensions/CodeBlock/index.spec.js

@@ -10,6 +10,20 @@ context('/api/extensions/code-block', () => {
     })
   })
 
+  it('should parse code blocks correctly', () => {
+    cy.get('.ProseMirror').then(([{ editor }]) => {
+      editor.setContent('<pre><code>Example Text</code></pre>')
+      expect(editor.html()).to.eq('<pre><code>Example Text</code></pre>')
+    })
+  })
+
+  it('should parse code blocks with language correctly', () => {
+    cy.get('.ProseMirror').then(([{ editor }]) => {
+      editor.setContent('<pre><code class="language-css">Example Text</code></pre>')
+      expect(editor.html()).to.eq('<pre><code class="language-css">Example Text</code></pre>')
+    })
+  })
+
   it('the button should make the selected line a code block', () => {
     cy.get('.demo__preview button:first')
       .click()