Unit testing signing of a certificate

Im probably overthinking this but I have a certificate that I have to install on my web services server which is used to sign a specific request. When I run unit tests on a server that has this certificate my unit tests pass. When its not installed then it fails (duh right).

Im looking to create a simple certificate that I can use for each of my unit tests. Is there a simple way of doing this on the fly? Im just using this for unit tests so its not going to go anywhere I cant use mockq or any of the mocking frameworks so I am stuck creating it when the test runs.

Thanks