@Test
    void two_clusters_without_explicit_port_throws_exception() {
        Element cluster1Elem = DomBuilderTest.parse(
                "<container id='cluster1' version='1.0'>",
                nodesXml,
                "</container>");
        Element cluster2Elem = DomBuilderTest.parse(
                "<container id='cluster2' version='1.0'>",
                nodesXml,
                "</container>");
        try {
            createModel(root, cluster1Elem, cluster2Elem);
            fail("Expected exception");
        } catch (RuntimeException e) {
            assertThat(e.getMessage(), containsString("cannot reserve port"));
        }
    }
Tests for "core functionality" of the container model, e.g. ports, or the 'components' and 'bundles' configs.

Before adding a new test to this class, check if the test fits into one of the other existing subclasses
of {@link ContainerModelBuilderTestBase}. If not, consider creating a new subclass.

@author gjoranv
config-model/src/test/java/com/yahoo/vespa/model/container/xml/ContainerModelBuilderTest.java