Abstract: In order to test component class code with a conventional visual builder, a proxy component is created for each method, including constructors, in the component class code, which proxy component encapsulates the parameters of that method. In particular, parameters associated with a method are represented by properties of the proxy component created for that method. When each proxy component is displayed on the GUI of the visual builder, its properties, and consequently, the parameters of the underlying method, are visually editable and can be bound visually to other component properties using, for example, a mechanism in a conventional visual builder which links objects. Exceptions which occur during operation of the method are treated as events and can be visually passed to other components. Therefore, a program can be visually constructed and parameterized for runtime operation.