import java.io.File;
import java.util.Optional;
import java.util.Set;

final class EmptyFileCollection extends AbstractFileCollection {
    public static final FileCollectionInternal INSTANCE = new EmptyFileCollection(DEFAULT_COLLECTION_DISPLAY_NAME);

    private final String displayName;

    public EmptyFileCollection(String displayName) {
        this.displayName = displayName;
    }

    @Override

import static org.gradle.api.internal.file.TestFiles.fileCollectionFactory

class EmptyFileCollectionExecutionTimeValueTest extends Specification {

    def "EmptyFileCollection supports execution time value"() {
        given:
        def collection = new EmptyFileCollection("foo")

        when:
        def executionTimeValue = collection.calculateExecutionTimeValue()

        then:
        executionTimeValue.present

            return empty();
        } else {
            return new EmptyFileCollection(displayName);
        }
    }

    /**
     * Creates an empty {@link FileCollection}
     */
    static FileCollectionInternal empty() {
        return EmptyFileCollection.INSTANCE;
    }

    /**
     * Creates a {@link FileCollection} with the given files as content.
     *

    }

    @Override
    public FileCollectionInternal fixed(String displayName, File... files) {
        if (files.length == 0) {
            return new EmptyFileCollection(displayName);
        }
        return new FixedFileCollection(displayName, taskDependencyFactory, patternSetFactory, ImmutableSet.copyOf(files));
    }

    @Override