AbstractThe debate between those who prefer formal methods and those who advocate the use of reliability‐growth models in the assessment of software reliability continues. Some issues arising from this conflict are raised and discussed, beginning with the definition of quantified software reliability. After arguing that the stochastic modelling approach is conceptually sound, its possible relationship with the structure of the software is discussed. Evidence that certain structural counts can be used in place of time as the argument in reliability growth models is reported. The question of the extent to which the many non‐stochastic metrics now available contribute to software reliability quantification is aired. A relationship between reliability and a hierarchy of coverage metrics is reported, which may help to draw together the modellers and the test