They're not deploying untested software, if that's what you're asking. They most likely simply deploy each change when it is ready, rather than building up work

They're not deploying untested software, if that's what you're asking. They most likely simply deploy each change when it is ready, rather than building up work-in-progress and deploying many changes at the same time. It's a lot safer to change one thing at a time, see https://www.goodreads.com/en/book/show/35747076-accelerate https://www.goodreads.com/en/book/show/35747076-accelerate. Releasing changes as soon as they are ready can also enable them to gather feedback faster - in this sense they would be iteratively 'testing' the product.