I have been building a test automation project for a customer that uses Microsoft Dynamics 365 as their business platform.

All test cases I have been building for them are happy cases, the chance for them to go wrong is very very remote. 

* If tests do not catch any bugs, they serve no purpose but to provide confidence to the management that "happy cases" are working.

There are many many more tests we can potentially implement for our customer, such as:

* Negative tests
* Tests with mutation

But to our customers, hiring us to implement those tests will cost them quite a bit money, and that is probably the primary reason that stops them from doing it.

It is really hard to convince someone to implement a prevention when the problem has not happened yet. 

Any suggestions?