To evaluate and diagnose leaner's learning progress, assessment is important for teachers in their teaching. Recently, with widespread of information and technology developed, many teachers have strong intention to adopt computerized tests. In addition, in the test, a diagnostic information with remedial learning is also an essential mechanism in self-directed learning for learners. However, making computerized tests with diagnostic messages is a tedious and complex task for most teachers who have no sophisticated programming skills. This study aims to develop a construction tool for teachers to create their own web- based diagnostic multimedia tests. Once the test created with related concept structures followed by remedial resources, this tool automatically constructs a web-based module for testing. After an expert evaluation carried out later, this tool receives positive feedback from expected users in education.