mockSystemDevices create a directory similar to /sys/devices/ with some uncore PMUs.
Perf collector needs cgroup path to pass it's identity to perfEventOpen and ioctlSetInt.
Why does this work? Because in this scenario you need only a directory with reading rights.

Try using ioutil.TempDir("", "cgroup")

Separate this import.

Good one! 👍

You forgot about cleaning after the group. This leads to errors when reading stats.

Consider using this function

func (c *collector) deleteGroup(index int) {
	for name, files := range c.cpuFiles[index].cpuFiles {
		for cpu, file := range files {
			klog.V(5).Infof("Closing perf_event file descriptor for cgroup %q, event %q and CPU %d", c.cgroupPath, name, cpu)
			err := file.Close()
			if err != nil {
				klog.Warningf("Unable to close perf_event file descriptor for cgroup %q, event %q and CPU %d", c.cgroupPath, name, cpu)
			}
		}
	}
	delete(c.cpuFiles, index)
}

This is part of code from Destroy(). So it can look now like:

func (c *collector) Destroy() {
	c.uncore.Destroy()
	c.cpuFilesLock.Lock()
	defer c.cpuFilesLock.Unlock()

	for i, _ := range c.cpuFiles {
		c.deleteGroup(i)
	}
}

In my opinion, count the entire group or skip it. So in this scenario, you need also to delete the group like in collector.

I got: unable create config from perf event unable to transform event name event-that-not-exists to perf_event_attr: -4
Can it look better?

Similar to config error.

Similar to config error.

Delete this blank line.