This is a tricky one. I think for initial testing, as Doug says, the effects are not important. Really you are just testing that the copy motivates people to “add to box” and then proceed to checkout, and that all happens smoothly. At some point you would need to communicate animations to other stakeholders though.
In an ideal world, you’ll be working with talented front-end developers who are passionate about this stuff and will put the time in to making it happen. But the reality is sometimes a little different. I don’t work with devs - development is put to tender and outsourced to dev teams in ‘developing’ countries. To achieve something like the Simply Chocolate site would require a lot of documentation for devs (and the client for approval) and I’d need to mock the animations up. For such scenarios like this I use Adobe animate, or create an animated gif in photoshop.
Love the site, something to aspire to - thanks for sharing!