 For example, when testing a program that takes a user's personal details and verifies their credit card number, a developer may decide to add a magic string shortcut whereby entering the unlikely input of "***" as a credit card number would cause the program to automatically proceed as if the card were valid, without spending time verifying it.If the developer forgets to remove the magic string, and a user of the final program happens to enter "***" as a placeholder credit card number while filling in the form, the user would inadvertently trigger the hidden functionality.Often there are significant time constraints out of the developer's control right from the beginning of their involvement in a project.