### Question:
GlusterFileSystem extends FileSystem { public String toString() { return provider.getScheme() + ": }  @Override FileSystemProvider provider(); @Override void close(); @Override boolean isOpen(); @Override boolean isReadOnly(); @Override String getSeparator(); @Override Iterable<Path> getRootDirectories(); @Override Iterable<FileStore> getFileStores(); @Override Set<String> supportedFileAttributeViews(); @Override Path getPath(String s, String... strings); @Override PathMatcher getPathMatcher(String s); @Override UserPrincipalLookupService getUserPrincipalLookupService(); @Override WatchService newWatchService(); String toString();  }### Answer:
@Test public void testToString() { doReturn("gluster").when(mockFileSystemProvider).getScheme(); String string = "gluster: assertEquals(string, fileSystem.toString()); verify(mockFileSystemProvider).getScheme(); }