This is the best way to test your iPhone Battery.
Contact Apple to get the most accurate and complete battery status report. They will run a diagnostic on your device. You can make an appointment at any Apple Store to do this.
Apple will allow remote diagnostics on your device, and you can see the current battery status. If you are having problems with your battery, this is the best way to find out.
Although these tests are not necessary for new devices, they can be very helpful if your older devices have exhibited degraded performance. These tests can be helpful if you have a problem with your iPhone Repair's battery life.
Please share your findings with us below in the comments section. If you have any additional methods to obtain accurate and reliable battery reports using iOS devices, please share them with us.