I was taught when A/B testing every test should be based on a test hypothesis, e.g.
Control: Current Button (Blue) Test: White Button
"We believe that changing the CTA colour (British English spelling!) from Blue to White will increase Click rate because the button will be more noticeable due to the increased contrast ratio of white on our default black background. We will know this to be true when we see an increase in CTR % on the homepage to 95% statistical confidence."
Should I be writing a test hypothesis for a multivariate test. I want to find the optimum combination of button color, label and icon to increase Click Rate?