when:
        allowFileSystemAccess(true)
        def snapshot = read(someFile)
        then:
        assertIsMissingFileSnapshot(snapshot, someFile)

        when:
        allowFileSystemAccess(false)
        snapshot = read(someFile)
        then:
        assertIsMissingFileSnapshot(snapshot, someFile)

        def missingSubfile = someFile.file("subfile")
        when:
        snapshot = read(missingSubfile)
        then:

        assert snapshot.name == file.name
        assert snapshot.type == FileType.RegularFile
        assert snapshot.hash == hashFile(file)
    }

    void assertIsMissingFileSnapshot(FileSystemLocationSnapshot snapshot, File file) {
        assert snapshot.absolutePath == file.absolutePath
        assert snapshot.name == file.name
        assert snapshot.type == FileType.Missing
    }