Abstract The report is a result of an activity within the project Centre for Object Technology (COT), case 2. In case 2 a number of pilot projects have been carried out to test the feasibility of using object technology within embedded software. Some of the pilot projects have resulted in proto-types that are currently being developed into production versions. To assure a high quality in the product it was decided to carry out an ac-tivity regarding issues in testing OO software. The purpose of this report is to discuss the issues of testing object-oriented software. It is often claimed that testing of OO software is radically different form testing traditional software developed using imperative/procedural programming. Other authors claim that there is no difference. In this report we will attempt to give an answer to these questions (or at least initiate a discussion).