Views on testing fonts?

I am interested to hear views on offering fonts for testing purposes?

I am often asked can I supply my font software so the designer, design company or agency can test the font out before making a decision whether to purchase.

In most cases these tests will be shown to the client as part of a presentation pitch.

Although I've agreed to this on many occasions I've found it rarely results in a sale.

This is a bit like the debate over the ethics of designers free-pitching.

All views welcome.