In general, a component-based system uses only a part of the functions of its software components. Therefore, precise structural testing for components requires to specify what functions of the components are used in the system. In addition, in the case with an object-oriented component, some existing studies point out that testing of all possible bindings between a call site and the methods that the site may invoke is extremely ineffective. In this paper, we propose a method for precisely estimating test coverage of components on an object-oriented framework by using its deployment descriptor and evaluate its effectiveness.