Grey box completion and validation

Grey box completion and validation is a way to check if something is correct or not. It's like when you do a puzzle - you can see some of the pieces, but there are parts you can't see until you have put the pieces together. Grey box completion and validation works the same way: It looks at all the pieces (or data) you have, and checks that everything makes sense. If it doesn't make sense, then it can tell you and you can look for any mistakes you might have made.