- Add TestMappingSliceOfCustomBindUnmarshalerElementsUri with validation for multiple elements, single element, and error cases
- Add TestMappingSliceOfCustomBindUnmarshalerElementsForm with comprehensive test coverage including large slices
- Add TestMappingArrayOfCustomBindUnmarshalerElementsUri with exact array size validation and error handling
- Add TestMappingArrayOfCustomBindUnmarshalerElementsForm with proper error case coverage
- Enhance test coverage for custom BindUnmarshaler slice and array functionality