private ShareMembershipManager mockStaleMember() {
        ShareMembershipManager membershipManager = createMemberInStableState();
        doNothing().when(subscriptionState).assignFromSubscribed(any());
        when(subscriptionState.hasAutoAssignedPartitions()).thenReturn(true);
        membershipManager.transitionToSendingLeaveGroup(true);
        membershipManager.onHeartbeatRequestSent();
        return membershipManager;
    }
Member that intentionally leaves the group (via unsubscribe) should release assignment,
reset epoch to -1, keep member ID, and transition to {@link MemberState#LEAVING} to send out a
heartbeat with the leave epoch. Once the heartbeat request is sent out, the member should
transition to {@link MemberState#UNSUBSCRIBED}
clients/src/test/java/org/apache/kafka/clients/consumer/internals/ShareMembershipManagerTest.java