Thanks for the test case, that highlighted the problem nicely.

I do agree blindly delegating to EqualsHelper is incorrect. The SinglePropertyMapper should hold a reference to a type or descriptor for which it delegates comparisons to, allowing not only this BigDecimal use case to work as intended; however, to support custom type implementation equality checks appropriately.

In order to avoid any performance issues, we'll attempt to cache the Type up-front during construction of these mappers and delegate there for comparison needs to avoid this issue with BigDecimal & potentially other types.