When you create a Pega unit test case for a flow or case type, you run the flow or case type and enter data for assignments and decisions as you step through the flow or case type.

You can start recording at any time, and you can stop recording at any time to create a test case with all the data that you entered up until the point that you stopped recording.

Additionally, you can use the following new assertions

• Assigned to – Verifies that the case is routed to the appropriate operator or work queue.
• Case status – Verifies the status of a case.
• Attachment exists – Verifies that an attachment exists.
• Case instance count – Verifies the number of case types, such as child cases, that are created when the test case runs.

For more information, see PegaUnit test cases for flows and case types.

If parent case is opening the child cases in the same tab then you can proceed and create test cases to record both parent and child case.

If child case is spinning a new tab then we cant record such child cases from parent case, support of these use cases is not available right now in pega unit.