How to test server side validation in AngularJS applications

I'm developing a Spring + AngularJS 1.x application. For test automation, I'm thinking to use a functional testing tool like Selenium.

Client side form validation can be easily tested using the tool. But I was wondering how to test server side validation. If AngularJS had some setting, using which client side validation could be disabled, then my same test scripts could be used for server side testing. Otherwise, I think I'll have to write server test scripts using a separate, API testing tool. Not only will that double the effort, but also I 'll have to simulate using CORS, CSRF etc., which might not be a great reality-check.

Like to hear recommendations.

(Note: In AngularJS, if we submit the form even if client side errors are displayed, AngularJS does not populate the fields)