}

    void canConvertToCollectionTypes() {
        File file = new File("f1")
        TestFileCollection collection = new TestFileCollection(file)

        expect:
        collection as Collection == toList(file)
        collection as Set == toLinkedSet(file)
        collection as List == toList(file)
    }

    void toFileTreeReturnsSingletonTreeForEachFileInCollection() {

        expect:
        def collection = factory.fixed("some collection")
        collection.files.empty
        collection.buildDependencies.getDependencies(null).empty
        collection.visitStructure(new BrokenVisitor())
        collection.toString() == "some collection"
    }

        collection.contains(file2)
    }

    def "does not contain file when no source collection contains file"() {
        def source1 = new TestFileCollection(file1)
        def source2 = new TestFileCollection(file2)
        def collection = new TestCompositeFileCollection(source1, source2)

        expect:
        !collection.contains(file3)
    }

    def "is empty when has no source collections"() {
        expect:

    return Collections.unmodifiableCollection(collection);
  }

  @Override
  public void clear() {
    // Clear each collection, to make previously returned collections empty.
    for (Collection<V> collection : map.values()) {
      collection.clear();
    }
    map.clear();
    totalSize = 0;
  }

  // Views

  /**
   * {@inheritDoc}
   *

        when:
        collection.convention(src1)
        collection.from = src2
        collection.convention(src3 + collection)
        collection.from = collection + src4

        then:
        collection.files as List == [file2, file4]
        collection.explicit

        when:
        collection.unset()
        collection.convention(collection + src5)

        then:

     *
     * <p>The collection is not live. The provided {@link Collection} is queried on construction and discarded.
     */
    FileCollectionInternal fixed(String displayName, Collection<File> files);

    /**
     * Creates a {@link FileCollection} with the given files as content.
     *
     * <p>The collection is live and resolves the files on each query.
     *

    while (entryIterator.hasNext()) {
      Entry<K, Collection<V>> entry = entryIterator.next();
      K key = entry.getKey();
      Collection<V> collection = filterCollection(entry.getValue(), new ValuePredicate(key));
      if (!collection.isEmpty()
          && predicate.apply(Maps.<K, Collection<V>>immutableEntry(key, collection))) {
        if (collection.size() == entry.getValue().size()) {
          entryIterator.remove();
        } else {

codehaus.plexus.PlexusContainer, String); public boolean add(Object); public void add(int, Object); public boolean addAll(java.util.Collection); public boolean addAll(int, java.util.Collection); public void clear(); public boolean remove(Object); public Object remove(int); public boolean removeAll(java.util.Collection); public boolean retainAll(java.util.Collection); public Object set(int, Object); protected final java.util.List checkedGetList() throws org.codehaus.plexus.component.repository.ex...

   */
  Collection<V> values();

  /**
   * Returns a view collection of all key-value pairs contained in this multimap, as {@link Entry}
   * instances.
   *
   * <p>Changes to the returned collection or the entries it contains will update the underlying
   * multimap, and vice versa. However, <i>adding</i> to the returned collection is not possible.
   */

        Visit,
        // Visitor is not interested in the contents of the collection, but would like to receive the source and other metadata
        NoContents
    }

    /**
     * Called when starting to visit a file collection. Can return true to continue with visiting or false to skip this collection and its contents.
     *