Cannot set Assigned Approver as ‘Queue:Queue_Name’ in Approval Steps of Approval Process using Metadata API

Question

If the queue does not contains parent Object as supported Object but doesnot contains childObject as supported Object user can set Queue as approver for a approval process created on child Object. But same does not works with API.

Steps for replication

1. Create a parent object 'ParentObj__c'.
2. Create a child Object'ChildObj__c' with Parent as 'ParentObj__c'.
3. Create a queue 'TestQueue' and add 'ParentObj__c' to its list of supported Objects.
4. Create a approval process on 'childobj__c' using UI. ApprocalProcess -> Approval Process Jump Start Wizard -> Select Approver -> automatically assign to queue. -> Select TestQueue from Lookup -> Save
5. Approval process is created successfully
6. When the same approval process 'childobj__c.a1.approvalProcess' is create using Metadata API, Approval process is not created. The user gets the below error :- ' Approval step Step_1 references Test_Queue, which doesn't exist as a queue .'

Answer 1

Well, after setting the bounty I tried some other things. Turns out the queue didn't have the proper sObject assigned.

So, for instance, if you want to have an approval process on a custom object, make sure that object is selected in the Supported Objects section on the Edit page of the queue. Note that detail parts of master-detail relationship are not selectable, you have to select the parent.