Is it possible for me to test my webapp in China to see what is blocked?

I work for a company and we are setting up a customer base in China to use it. We are having a couple of issues with content being blocked and breaking the site. We need to find a VPN to emulate the fact that we are based in China when looking at the website.

I have tried pureVPN and tunnelbear but they don't seem to be affected by the firewall that blocks everything. I understand that this is the opposite of what a lot of people use VPNs for when it comes to China but I need to find a way around this in order to get our app working correctly.