With the increasing application of software in systems, especially safety- or even life-critical systems, it is no longer sufficient for the software developer to rely solely on testing the code produced. Testing must begin with the specification of requirements, continue on the design and finally on the implemented system. This book gives guidance on how testing can be carried out at each of the stages of software development. It does this by looking at the development process from four viewpoints: that of the intended user of the system, of its designers, of its programmers, and of the manager responsible for development. The product of each stage of development is individually examined to see how it can be checked for correctness and consistency with earlier specifications. References are given to techniques available to the software developer and there are many helpful checklists. The contributors are all members of the British Computer Society's Working Group on Testing, and between them have an impressive breadth of practical experience in the commercial development of small and large software systems. Their combined experience makes this a most valuable book for the computing professional.