public HostProvisioner provisioner() {
        if (provisioner instanceof ProvisionerAdapter)
            return ((ProvisionerAdapter)provisioner).provisioner();
        return provisioner;
    }
Helper class which sets up a system with multiple hosts.
Usage:
<code>
    VespaModelTester tester = new VespaModelTester();
    tester.addHosts(count, flavor);
    ... add more nodes
    VespaModel model = tester.createModel(servicesString);
    ... assert on model
</code>

@author bratseth
config-model/src/test/java/com/yahoo/vespa/model/test/VespaModelTester.java