To run the full set of chart-verifier tests you will need access to an OpenShift cluster, so the chart installation and its chart test(s) can be executed. You can disable these OpenShift tests through command line options, but they will need to run successfully for certification to be approved.
As a Red Hat partner, you have free access to an OpenShift Container Platform subscription that you can use to install a cluster in your own lab. To learn more about the benefit of software access as part of Red Hat Partner Connect, see the program guide.
There are other options to get access to an OpenShift environment, such as a local (e.g. laptop) environment or a hosted environment managed by Red Hat. See openshift.com/try for details and restrictions. Keep in mind that the Developer Sandbox is not an adequate option for the purposes of certification.