@Override
    public RebuildResult startHosts(Collection<Node> hosts) {
        List<Node> successes = new ArrayList<>();
        for (Node host : hosts) {
            if ( ! host.type().isHost()) throw new IllegalArgumentException(host + " is not a host");
            if (rebuildsStartingHost.remove(host.hostname())) {
                successes.add(host.withWantToRetire(host.status().wantToRetire(), host.status().wantToDeprovision(),
                                                  false, false, false, Agent.system, Instant.ofEpochMilli(123)));
            }
        }
        return new RebuildResult(successes, new LinkedHashMap<>());
    }
Returns whether given behaviour is active for this invocation
node-repository/src/main/java/com/yahoo/vespa/hosted/provision/testutils/MockHostProvisioner.java