How to create a Epic Link via TestKit

I’m trying to create a issue epic link via testkit.
My plan was to try to enable jira agile (greenhopper) and then add a epic link custom field to a issue.

I’m not sure how to install greenhopper via testkit or if it is even possible.
This does not seem to do anything:

And this throws, not found because the epic link custom field does not exist:

        IssueFields issueFields = new IssueFields();
        issueFields.customField(10103L, String.valueOf(value));
        backdoor.issues().setIssueFields(issueKey, issueFields);

Can someone help me to create a epic link via testkit for testing purposes?