add a lot more parseDOM tests to all extensions

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

@@ -9,6 +9,20 @@ context('/api/extensions/hard-break', () => {
     })
   })
 
+  it('should parse hard breaks correctly', () => {
+    cy.get('.ProseMirror').then(([{ editor }]) => {
+      editor.setContent('<p>Example<br>Text</p>')
+      expect(editor.html()).to.eq('<p>Example<br>Text</p>')
+    })
+  })
+
+  it('should parse hard breaks with self-closing tag correctly', () => {
+    cy.get('.ProseMirror').then(([{ editor }]) => {
+      editor.setContent('<p>Example<br />Text</p>')
+      expect(editor.html()).to.eq('<p>Example<br>Text</p>')
+    })
+  })
+
   it('the button should add a line break', () => {
     cy.get('.ProseMirror br')
       .should('not.exist')