private Set<HostSpec> prepare(ApplicationId application, Capacity capacity, ProvisioningTester tester) {
        return new HashSet<>(tester.prepare(application, cluster(), capacity));
    }
When increasing the number of groups without changing node count, we need to provison new nodes for
the new groups since although we can remove nodes from existing groups without losing data we
cannot do so without losing coverage.
node-repository/src/test/java/com/yahoo/vespa/hosted/provision/provisioning/MultigroupProvisioningTest.java