### Question:
GlusterFileSystemProvider extends FileSystemProvider { long getUsableSpace(long volptr) throws IOException { statvfs buf = new statvfs(); GLFS.glfs_statvfs(volptr, "/", buf); return buf.f_bsize * buf.f_bavail; }  @Override String getScheme(); @Override FileSystem newFileSystem(URI uri, Map<String, ?> stringMap); @Override FileSystem getFileSystem(URI uri); @Override Path getPath(URI uri); @Override SeekableByteChannel newByteChannel(Path path, Set<? extends OpenOption> openOptions, FileAttribute<?>... fileAttributes); @Override FileChannel newFileChannel(Path path, Set<? extends OpenOption> options, FileAttribute<?>... attrs); @Override DirectoryStream<Path> newDirectoryStream(Path path, DirectoryStream.Filter<? super Path> filter); @Override void createDirectory(Path path, FileAttribute<?>... fileAttributes); @Override void delete(Path path); @Override void copy(Path path, Path path2, CopyOption... copyOptions); @Override void move(Path path, Path path2, CopyOption... copyOptions); @Override boolean isSameFile(Path path, Path path2); @Override boolean isHidden(Path path); @Override FileStore getFileStore(Path path); @Override void checkAccess(Path path, AccessMode... accessModes); @Override V getFileAttributeView(Path path, Class<V> vClass, LinkOption... linkOptions); @Override A readAttributes(Path path, Class<A> type, LinkOption... linkOptions); @Override Map<String, Object> readAttributes(Path path, String s, LinkOption... linkOptions); @Override void setAttribute(Path path, String s, Object o, LinkOption... linkOptions); @Override Path readSymbolicLink(Path link); @Override void createSymbolicLink(Path link, Path target, FileAttribute<?>... attrs); static final String GLUSTER; static final int GLUSTERD_PORT; static final String TCP; }### Answer:
@Test public void testGetUsableSpace() throws Exception { mockStatic(GLFS.class); long volptr = 1234l; String path = "/"; statvfs buf = new statvfs(); buf.f_bsize = 2; buf.f_bavail = 1000000l; whenNew(statvfs.class).withNoArguments().thenReturn(buf); when(GLFS.glfs_statvfs(volptr, path, buf)).thenReturn(0); long usableSpace = provider.getUsableSpace(volptr); verifyStatic(); GLFS.glfs_statvfs(volptr, path, buf); verifyNew(statvfs.class).withNoArguments(); assertEquals(buf.f_bsize * buf.f_bavail, usableSpace); }