Summary:
Test everything, test everything a lot.
I know this seems obvious, but don't underestimate the importance of it.
Introduction:
The reason I bring this up is that recently I was shopping online and seen that there was free delivery offer for those in Germany, but Ireland was the only option available in the delivery field.
While this made no difference to me, there are a few things to note:This online shop could only deliver to Ireland - and removing the option of a global audience.
The shop offered a special promotion but it was impossible to claim this, potentially creating a sense of frustration.While this may not seem like a huge issue, it's only a drop down list after all.
It does raise the question.
How long has this shop not been able to receive orders from those outside of Ireland?This feedback was given and the site has since been updated.
Where to start?
A good place to start is to consider some testing personas.Who is your audience? and ask the question. Can this person perform this action?
Computers are notoriously unreliable, and we have all at some point had the expierence that if "I do a, b will happen, and instead c happened".That's why after every change it is always recommended to try and test it, to make sure everything works as expected.
This advice applies to everyone, whether you are making your own site on Wordpress, creating your own e-commerce site with Shopify.It is always a good idea to test.
How to test?
I know having every device to test on is difficult. But somewhere like Lambdatest  also a great alternative.
This allows you to have access to both iOS and android devices as well as Mac, Windows and Linux.It is on the expensive side, but by no means is it needed as a rolling subscription.
If you are only testing your site, a since month should cover all your needs.
Family and friends are always a good place to start too.A much more afforable offer, but the price of this is having people you know critique your site.