diff --git a/docs/src/demos/Extensions/Highlight/index.spec.js b/docs/src/demos/Extensions/Highlight/index.spec.js
index eb2f7e0c..7321e2d0 100644
--- a/docs/src/demos/Extensions/Highlight/index.spec.js
+++ b/docs/src/demos/Extensions/Highlight/index.spec.js
@@ -19,6 +19,61 @@ context('/api/extensions/highlight', () => {
       .should('contain', 'Example Text')
   })
 
+  it('should highlight the text in a specific color', () => {
+    cy.get('.demo__preview button:nth-child(2)')
+      .click()
+
+    cy.get('.ProseMirror')
+      .find('mark')
+      .should('contain', 'Example Text')
+      .should('have.css', 'background-color', 'rgb(255, 0, 0)')
+  })
+
+  it('should update the attributes of existing marks', () => {
+    cy.get('.ProseMirror').then(([{ editor }]) => {
+      editor.setContent('<p><mark style="background-color: blue;">Example Text</mark></p>')
+      editor.selectAll()
+
+      cy.get('.ProseMirror')
+        .find('mark')
+        .should('have.css', 'background-color', 'rgb(0, 0, 255)')
+
+      cy.get('.demo__preview button:nth-child(2)')
+        .click()
+
+      cy.get('.ProseMirror')
+        .find('mark')
+        .should('have.css', 'background-color', 'rgb(255, 0, 0)')
+    })
+  })
+
+  it('should remove existing marks with the same attributes', () => {
+    cy.get('.ProseMirror').then(([{ editor }]) => {
+      editor.setContent('<p><mark style="background-color: red;">Example Text</mark></p>')
+      editor.selectAll()
+
+      cy.get('.ProseMirror')
+        .find('mark')
+        .should('have.css', 'background-color', 'rgb(255, 0, 0)')
+
+      cy.get('.demo__preview button:nth-child(2)')
+        .click()
+
+      cy.get('.ProseMirror')
+        .find('mark')
+        .should('not.exist')
+    })
+  })
+
+  it('the button should highlight the selected text', () => {
+    cy.get('.demo__preview button:first')
+      .click()
+
+    cy.get('.ProseMirror')
+      .find('mark')
+      .should('contain', 'Example Text')
+  })
+
   it('the button should toggle the selected text highlighted', () => {
     cy.get('.demo__preview button:first')
       .click()