In this paper, we present a blended e-learning experience consisting of supplying an undergraduate student population (in addition to traditional on-site classes) with a learning tool called OOPS (Object Oriented Programming System) and a testing system called SIETTE. OOPS is a problem-solving environment in which students can resolve Object Oriented Programming exercises. The system applies an assessment for learning strategy where students are formatively assessed, i.e. OOPS diagnoses their knowledge level but also generates feedback and hints to help students to understand and overcome their misconceptions and to reinforce correctly learnt concepts. In conjunction with OOPS, we have used SIETTE, a web-based assessment system in which students can take tests and teachers can construct them Subsequently, we have explored whether or not the use of OOPS contributes to improve the students’ knowledge about Object Oriented Programming. 2009 Elsevier B.V. All rights reserved.