Declarative Rollup Summary - error

I want to create a Declarative Rollup Summary , but I hit the following error :

dlrs_pse_AssignmentTest.testTrigger System.DmlException: Insert failed. First exception on row 0; first error: FIELD_CUSTOM_VALIDATION_EXCEPTION, Bill Rate is required: [pse__Bill_Rate__c] Class.dlrs.RollupService.testHandler: line 282, column 1 Class.dlrs_pse_AssignmentTest.testTrigger: line 11, column 1

Scenarios is as follow :

• Parent object : pse__Milestone__c
  Child Object : pse__Assignment__c
  Relationship field : pse__Milestone__c
  Field to aggregate : Days_Active__c
  Aggregate result field : Days_Active_Roll_Up__c

Manage child trigger :

/** * Auto Generated and Deployed by the Declarative Lookup Rollup Summaries Tool package (dlrs) **/ trigger dlrs_pse_AssignmentTrigger on pse__Assignment__c (before delete, before insert, before update, after delete, after insert, after undelete, after update) { dlrs.RollupService.triggerHandler(pse__Assignment__c.SObjectType); } /** * Auto Generated and Deployed by the Declarative Lookup Rollup Summaries Tool package (dlrs) **/ @IsTest private class dlrs_pse_AssignmentTest { @IsTest private static void testTrigger() { // Force the dlrs_pse_AssignmentTrigger to be invoked, fails the test if org config or other Apex code prevents this. dlrs.RollupService.testHandler(new pse__Assignment__c()); } }

Why getting declarative lookup rollup summaries? What might be the issue? I have deactivated the validation rule but still have this error.