I've downloaded a ubuntu image and I would like to run some tests against that image. How can I test the image on my machine? What tests are available to run and how can I report my results and bugs?
Assuming you downloaded a non-release image (that is to say, an image intended for testing), the ISO Tracker contains a list of tests meant to be executed for the image. For example, a daily ubuntu amd64 image has, as of this writing, 21 testcases representing different scenarios for installing and using the ubuntu image on your machine.
These tests can be seen, executed and reported all using the ISO Tracker interface. A tutorial on using the tracker can be found here. You will need a launchpad account to login and report results. Each image contains download links for the image, instructions for reporting bugs, and a form to submit results. In general you can utilize your machine, or a virtual machine for testing. Real hardware testing is encouraged, but don't overwrite your current installation and data unless you understand what your doing! Virtual machines such as Virtualbox, Vmware player, or KVM are common for virtualized testing.
If you are using a release image of ubuntu and encounter a bug, you are encouraged instead to file the problem as a bug.
In addition to Neojames answer, you can use virtualbox to install it and run your tests on it without having the need for reboot