allowFileSystemAccess(true)
        def childSnapshot = read(childDir)

        when:
        def parentSnapshot = read(parentDir)
        def index = SnapshotUtil.indexByAbsolutePath(parentSnapshot)

        then:
        index[childDir.absolutePath].is(childSnapshot)
    }

    def "reuses cached descendant tree when it has siblings on read"() {
        given:

        Map<String, FileSystemLocationSnapshot> beforeExecutionIndex = indexByAbsolutePath(unfilteredBeforeExecution);
        if (beforeExecutionIndex.isEmpty()) {
            return unfilteredAfterExecution;
        }

        Map<String, FileSystemLocationSnapshot> previousIndex = previous != null
            ? indexByAbsolutePath(previous)
            : ImmutableMap.of();

        }

        @Override
        public FileCollectionInternal createDelegate() {
            List<File> outputs = previousOutputs.values().stream()
                .map(SnapshotUtil::indexByAbsolutePath)
                .map(Map::keySet)
                .flatMap(Collection::stream)
                .map(File::new)
                .collect(Collectors.toList());

        def snapshot = directorySnapshotter.snapshot(rootDir.absolutePath, null, knownSnapshots, unfilteredSubSnapshotsCollector)

        then:
        0 * _

        when:
        def visited = SnapshotUtil.indexByAbsolutePath(snapshot)

        then:
        visited[rootDir.absolutePath] instanceof DirectorySnapshot
        visited[rootTextFile.absolutePath] instanceof RegularFileSnapshot