How can we check our push data?

You can check your push data once it arrives and, Insider handles it. The following example displays a payload of a push received by Insider:

I/[INSIDER][pushReceived]: {thread-id=insider-test-push, source=Insider, uuy=ytyu, badge=0, title=mytest, 
                                    channel={"channel_name":"Default Channel","importance":4,"led_color":1,"sound":1,"id":1,"is_badge_enabled":1,
                                            "is_vibration_enabled":1,"is_visible_on_lock_screen":1}, 
                                    message=test}