In order to introduce learning cases with real-world contexts to the Computer Science students in their early stage of learning, a set of Web applications that utilize Web services are simplified and customized to demonstrate the core concept of high-level test-driven learning methodology. Four e-commerce Web applications were implemented for this project. These applications show how real-world Web services work and interact with each other. By systematically planting a number of errors into the services, we created a learning environment for the students to understand the system structure and basic programming through their critical thinking. A goal is to keep students' interest in computer science. In doing so, a set of features that help students observe the systems' behavior are designed, and collectively formed a pattern of user interface "the Learner's Corner."