Adding HTML form validation to FAQ, closes #1824 (#1919)

source/faq/questions/using-cypress-faq.md

@@ -203,6 +203,23 @@ describe('The Document Metadata', () => {
 })
 ```
 
+## {% fa fa-angle-right %} Can I check that a form's HTML form validation is shown when an input is invalid?
+
+You certainly can.
+
+```javascript
+it('check validation message on invalid input', () => {
+  cy.get('input:invalid').should('have.length', 0)
+  cy.get('[type="email"]').type('not_an_email')
+  cy.get('[type="submit"]').click()
+  cy.get('input:invalid').should('have.length', 1)
+  cy.get('[type="email"]').then(($input) => {
+    expect($input[0].validationMessage).to.eq('I expect an email!')
+  })
+})
+```
+
+
 ## {% fa fa-angle-right %} Can I throttle network speeds using Cypress?
 
 You can throttle your network connection by accessing your Developer Tools Network panel. Additionally, you can add your own custom presets by selecting **Custom > Add** from the Network Conditions drawer.