You can test the design-time behavior of a component after you install it on the Tool palette. This is particularly useful for debugging newly created components, but the same technique works with any component, whether or not it is on the Tool palette. For information on testing components that have not yet been installed, see Testing uninstalled components. 

Testing your components after installing allows you to debug the component that only generates design-time exceptions when dropped on a form.

1. Choose ProjectOptionsDebugger and set the Debug Source Path to point to the component's source file.
2. Then select ToolsOptions. On the Debugger OptionsBorland DebuggersLanguage Exceptions page, enable the exceptions you want to track.
3. Open the component source file and set breakpoints.
4. Select RunParameters and set the Host Application field to the name and location of the Delphi executable file.
5. In the Run Parameters dialog, click the Load button to start a second instance of Delphi.
6. Then drop the components to be tested on the form, which should break on your breakpoints in the source.