Service-Oriented Architecture (SOA) fosters the development of loosely coupled applications. Web services have been favored as a promising technology to implement SOAs. Since web services are often involved in complex business processes and safety-critical systems, it is important that they are of high level of reliability. In this paper a strategy for event-based testing of web services is introduced which enables a systematic test case generation for structural testing with the focus on code coverage. The novelty of the approach stems from its integration of an event-based view with a coverage-based view. This forms a combination of black- and white-box testing leading to grey-box testing. A bank service example illustrates the strategy.