Relying on customers to do the testing isn't a great idea

I agree that customers might know their features the best, and as such, are the presumable testers. But can you rely 100% that testing isn't squeezed between deadlines of an implementation, and, in addition, between deadlines of their daily work? And still, in what way does their testing contribute to a more effective test effort in the future? How structured and reproducible will it be?

Posing these questions answers them already. It isn't a great idea, in general, to rely on customers testing if you want to improve your development practices. Having said that, this doesn't mean that customers should not be included; by all means, incorporate them in setting up your automated tests. We will elaborate on that more later.