Input-Predicate/Output (IP/O)_{n}-chains coverage criterion, originally proposed for black-box testing of telecommunications software, is adapted to white-box testing of programs written in block-structured languages. This criterion is based on the analysis of the effects of inputs on predicates and outputs in a program. It requires that each such effect in a program is examined at least once during testing and thus provides a means of capturing the implemented functionality and checking the consistency of the program with respect to its functional requirements. It is shown that its fault-detecting ability is higher than the all-uses criterion, and compares favorably with the required k-tuples^+ criterion.