How can I subgroup bugs grouped in an epic in jira

My scenario : We are in the integration testing phase . We would like to group all bugs in this phase on JIRA .

My problem : I wanted to create an epic called "testing phase" and group all bugs in the testing phase . But I also wanted to create a subgroup for "integration testing" and group all bugs in this integration testing phase . How do I do this .Can I use tasks under epic and do this ?

My research : I have tried searching for this in youtube , stackoverflow , etc but I have not been able to get an answer .

Look forward for your inputs and suggestions on this issue .