vboxmanage controlvm "pcfdev-v0.547.0" natpf1 "http,tcp,<your_host_ip>,8080,,80"
^^^ command line to configure the port forwarding rule to allow you to hit the test app webpage from a remote host.
pcfdev-v0.547.0 is the name of the VM PCF Dev creates. That will change with PCF Dev versions, so use
vboxmanage list runningvms to find the name or GUID of the VM you want to modify.