Web Services are increasingly becoming the standard for both Web-based commercial application as well as distributed scientific projects. Given the prominence of this technology, test methods and tools are required to ensure that robust systems are deployed. Testing is required not only to uncover existing problems but also to provide users with tools and metrics to compare similar solutions. In this paper, we propose WSInject, a fault injection tool for testing Web Services. WSInject is a script-driven fault injector able to inject both interface and communication faults. Unlike other Web Service fault injectors, WSInject allows users to combine several types of fault in one injection statement and is able to handle either single or composed services. We also present the results of preliminary experiments on a case study and show some revealed failures