Yes and no. In the common law systems (including both UK and US) where precedent is important and case law reigns supreme, what's actually written down may not mean what the words plainly say, if their interpretation has morphed through a series of incremental decisions. Hence the US's Fourth Amendment, among other things. Laws can be in place for years without being "tested in court" because nobody finds it worth the risk; and then it turns out that when they're tested they were invalid all along.

SO in some ways, having a written Constitution is worse, because you still are ultimately ruled by the centuries of caselaw and precedent, but you think the words actually mean something.