Ability to assert null values from Postgresql DB

[JuliaKaminskaya]

If null values appear in a select from a postgresql it cannot be compared correctly to an Examples table from test scenario. An assertion fails because "null" has null data type in the select and text data type in the test scenario.

It would be great to have a possibility to assert "null" values from DB to assert full select without any exclusions.

Please note that a types transformation to text during select is not working for null values. Assertion fails anyway.