Unit testing TRDX Report generation with Object datasource

We have a TRDX report with Object data source - that has Object = "XYZReport" and DataMember = "GetData()"

When the report is opened via viewer - everything runs fine.

When the report is rendered in a unit test method in a unit test project, it does not invoke GetData() method at all and renders empty report. The XYZReport class is in a separate Project/Classlibrary and Unit Test project references it. 

Any clue what could be happening and how we can resolve this?