}

    def "adds to collection"() {
        def list = [0]
        when:
        addToCollection(addToCollection(list, [1, 2]), [2, 3])
        then:
        list == [0, 1, 2, 2, 3]
    }

    def "adds empty list to collection"() {
        expect:
        addToCollection([], []) == []
        addToCollection([1], []) == [1]
    }

    def "adds to collection preventing nulls"() {
        when:

        }
        return dest;
    }

    public static <V, T extends Collection<? super V>> T addToCollection(T dest, Iterable<? extends V> src) {
        return addToCollection(dest, false, src);
    }

    @Deprecated
    public static <V, T extends Collection<? super V>> T addToCollection(T dest, boolean failOnNull, Iterable<? extends V>... srcs) {
        for (Iterable<? extends V> src : srcs) {

        }
        return dest;
    }

    public static <V, T extends Collection<? super V>> T addToCollection(T dest, Iterable<? extends V> src) {
        return addToCollection(dest, false, src);
    }

    @Deprecated
    public static <V, T extends Collection<? super V>> T addToCollection(T dest, boolean failOnNull, Iterable<? extends V>... srcs) {
        for (Iterable<? extends V> src : srcs) {

            throw new IllegalArgumentException("args == null!");
        }
        args(Arrays.asList(args));
        return this;
    }

    public ProcessArgumentsSpec args(Iterable<?> args) {
        GUtil.addToCollection(arguments, true, args);
        return this;
    }

    public ProcessArgumentsSpec setArgs(List<String> arguments) {
        this.arguments.clear();
        args(arguments);
        return this;
    }

    public Set<File> getApplicationClasspath() {
        return applicationClasspath;
    }

    @Override
    public WorkerProcessBuilder applicationModulePath(Iterable<File> files) {
        GUtil.addToCollection(applicationModulePath, files);
        return this;
    }

    @Override
    public Set<File> getApplicationModulePath() {
        return applicationModulePath;
    }

    @Override

        add(Arrays.asList(values));
        return this;
    }

    /**
     * Adds some start nodes.
     */
    public CachingDirectedGraphWalker<?, ?> add(Iterable<? extends N> values) {
        GUtil.addToCollection(startNodes, values);
        return this;
    }

    /**
     * Calculates the set of values of nodes reachable from the start nodes.
     */
    public Set<T> findValues() {
        try {

        source.addAll(Arrays.asList(srcDirs));
        return this;
    }

    @Override
    public SourceDirectorySet setSrcDirs(Iterable<?> srcPaths) {
        source.clear();
        GUtil.addToCollection(source, srcPaths);
        return this;
    }

    @Override
    public SourceDirectorySet source(SourceDirectorySet source) {
        this.source.add(source);
        return this;
    }