Test: increase rm-datasource module test coverage

## Why you need it?
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increase rm-datasource module test coverage

## How it could be?
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## Other related information
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Start by locating the rm-datasource module and reading its existing test classes and coverage configuration. Identify the module's untested behavior, then add focused tests and run the module's test and coverage commands. Done means the targeted rm-datasource coverage has increased with passing tests, but the issue does not specify a coverage goal.

Written by the indexing model from the issue text.