Over the last fifteen years, Web applications have evolved from the early simple and hyper-text based ones into the more complex, interactive, usable and adaptive applications of the new generations. New paradigms, architectures, and technologies for developing Web-based systems continuously emerge and transform this specific context. At the same time, new techniques and tools for effectively testing them have been proposed. This paper reports some relevant contributions about the Web application testing topic that appeared in the past editions of the Web Systems Evolution international symposium (WSE) and discusses some future trends for this specific field.