COMMUNICATIONS IN ALGEBRA, vol.46, no.9, pp.4052-4063, 2018 (SCI-Expanded)
A variety of rings including those that are Morita equivalent to local perfect rings, two by two upper triangular matrix rings over a division ring or certain rings arising in the framework of rings described by various test modules for injectivity satisfy a common property: there is a nonzero homomorphism between any two non-injective modules. In this paper, after settling a special case inspired by a concept due to Enochs as the first step, we provide a complete characterization of the rings of the title.