Is an iPod Touch 5th generation a good testing device for iOS (react-native) development in 2018
No, an iPod 5th gen would not work for testing your app for these reasons:


Software incapabilities. The 5th generation iPod came out in 2012 and is using a 32 bit architecture, therefore, it is unable to update to software requiring a 64 bit architecture. Which means it is stuck at iOS 9.


Why this matters:

iOS 10-11 brought many new features and speed improvements to all apple devices. If you are testing your product on a device that does not have these enhancements, you will not be able to provide a quality product to people using the newer versions of iOS




Processor problems. The iPod 5th gen came with Apple's A5 chip and a 32bit chip


Why this matters:

Plain and simple, your iPod will crash when it runs the app.