conf1.extendsFrom(conf2)
        conf2.extendsFrom(configuration)

        then:
        thrown InvalidUserDataException
    }

    def "reports cycle introduced by setExtends"() {
        def configuration = conf()
        def otherConf = conf("other")
        configuration.extendsFrom(otherConf)

        when:
        otherConf.setExtendsFrom([configuration])

        then:

    public String getName() {
        return name;
    }

    @Override
    public void extend(String configuration) {
        extendsFrom.add(configuration);
    }

    @Override
    public Set<String> getExtends() {
        return extendsFrom;
    }

    /**
     * The set of names of extended configurations, added via {@link #extend(String)}.
     *
     * @return The names of extended configurations.
     */
    Set<String> getExtends();

                    .attribute("name", configuration.getName())
                    .attribute("visibility", "public");
                if (configuration.getExtends().size() > 0) {
                    xmlWriter.attribute("extends", CollectionUtils.join(",", configuration.getExtends()));
                }
                xmlWriter.endElement();
            }
            xmlWriter.endElement();
        }

        boolean visible = configuration.getVisibility() == org.apache.ivy.core.module.descriptor.Configuration.Visibility.PUBLIC;
        List<String> extendsFrom = Lists.newArrayList(configuration.getExtends());
        result.add(new Configuration(name, transitive, visible, extendsFrom));
    }

    private void addDependency(List<IvyDependencyDescriptor> result, DependencyDescriptor dependencyDescriptor) {

            Set<String> configsToAdd = new HashSet<>();
            Configuration[] configs = md.getConfigurations();
            for (Configuration config : configs) {
                String[] ext = config.getExtends();
                for (String s : ext) {
                    if (conf.equals(s)) {
                        String configName = config.getName();
                        configsToAdd.add(configName);

Configuration(java.util.Map, java.util.Map, String, Configuration$Visibility, String, String[], boolean, String, org.apache.ivy.core.module.id.ModuleRevisionId); public final String getDeprecated(); public final String getDescription(); public final String[] getExtends(); public final String getName(); public Configuration$Visibility getVisibility(); public final boolean isTransitive(); public final org.apache.ivy.core.module.id.ModuleRevisionId getSourceModule(); public String toString(); public boolean equals(Object);...