Currently Mock table 'EMPNULLABLES' allows nulls in almost every column. It does not allow nulls in the primary key which is expected and the column 'ENAME' that is unexpected.
I realized that 'ENAME' column was declared as not nullable after debugging for quite some time a test where I was wrongly assuming that all columns of the table were nullable.
To avoid this kind of confusion in the future I propose to make 'ENAME' also nullable. The impact on existing tests is minimal.