I've seen some weirdness when running in CI because the tests run slightly faster in headless mode. Could be that? As for your use case, that can be a tricky one. It can be that the

.get(".react-loading-skeleton").should("not.exist")

assertion will pass before the loader element has even appeared Is there another element that will appear when the loader appears, but will remain after? You could assert on that one, then do the check for the loader