null condition (3 facts) - A situation where there normally exists one or more data items to process, but sometimes there are none
singleton condition (5 facts) - A situation in which there is normally more than one of something, but should be tested for the case where there is only one
software crisis (3 facts) - The situation that is said to have existed since a least the late 1970's, characterized by an inability of software developers to deliver good quality software on time and on budget