def test_empty(self):
        # single line
        cb = CifBlock.from_string("data_mwe\nloop_\n_tag\n ''")
        self.assertEqual(cb.data['_tag'][0], '')

        # multi line
        cb = CifBlock.from_string("data_mwe\nloop_\n_tag\n;\n;")
        self.assertEqual(cb.data['_tag'][0], '')

        cb2 = CifBlock.from_string(str(cb))
        self.assertEqual(cb, cb2)

    def test_double_quotes_and_underscore_data(self):
        cif_str = """data_test
_symmetry_space_group_name_H-M   "P -3 m 1"
_thing   '_annoying_data'"""
        cb = CifBlock.from_string(cif_str)
        self.assertEqual(cb["_symmetry_space_group_name_H-M"], "P -3 m 1")
        self.assertEqual(cb["_thing"], "_annoying_data")
        self.assertEqual(str(cb), cif_str.replace('"', "'"))

    def test_double_quoted_data(self):
        cif_str = """data_test
_thing   ' '_annoying_data''
_other   " "_more_annoying_data""
_more   ' "even more" ' """
        cb = CifBlock.from_string(cif_str)
        self.assertEqual(cb["_thing"], " '_annoying_data'")
        self.assertEqual(cb["_other"], ' "_more_annoying_data"')
        self.assertEqual(cb["_more"], ' "even more" ')

    def test_nested_fake_multiline_quotes(self):
        cif_str = """data_test
_thing
;
long quotes
 ;
 still in the quote
 ;
actually going to end now
;"""
        cb = CifBlock.from_string(cif_str)
        self.assertEqual(cb["_thing"], " long quotes  ;  still in the quote"
                                       "  ; actually going to end now")

    def test_to_string(self):
        with open(self.TEST_FILES_DIR / 'Graphite.cif') as f:
            s = f.read()
        c = CifBlock.from_string(s)
        cif_str_2 = str(CifBlock.from_string(str(c)))
        cif_str = """data_53781-ICSD
_database_code_ICSD   53781
_audit_creation_date   2003-04-01
_audit_update_record   2013-02-01
_chemical_name_systematic   Carbon
_chemical_formula_structural   C
_chemical_formula_sum   C1
_chemical_name_structure_type   Graphite(2H)
_chemical_name_mineral   'Graphite 2H'
_exptl_crystal_density_diffrn   2.22
_publ_section_title   'Structure of graphite'
loop_
 _citation_id
 _citation_journal_full
 _citation_year
 _citation_journal_volume
 _citation_page_first
 _citation_page_last
 _citation_journal_id_ASTM
  primary  'Physical Review (1,1893-132,1963/141,1966-188,1969)'
  1917  10  661  696  PHRVAO
loop_
 _publ_author_name
  'Hull, A.W.'
_cell_length_a   2.47
_cell_length_b   2.47
_cell_length_c   6.8
_cell_angle_alpha   90.
_cell_angle_beta   90.
_cell_angle_gamma   120.
_cell_volume   35.93
_cell_formula_units_Z   4
_symmetry_space_group_name_H-M   'P 63/m m c'
_symmetry_Int_Tables_number   194
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, x-y, -z+1/2'
  2  '-x+y, y, -z+1/2'
  3  '-y, -x, -z+1/2'
  4  '-x+y, -x, -z+1/2'
  5  '-y, x-y, -z+1/2'
  6  'x, y, -z+1/2'
  7  '-x, -x+y, z+1/2'
  8  'x-y, -y, z+1/2'
  9  'y, x, z+1/2'
  10  'x-y, x, z+1/2'
  11  'y, -x+y, z+1/2'
  12  '-x, -y, z+1/2'
  13  '-x, -x+y, -z'
  14  'x-y, -y, -z'
  15  'y, x, -z'
  16  'x-y, x, -z'
  17  'y, -x+y, -z'
  18  '-x, -y, -z'
  19  'x, x-y, z'
  20  '-x+y, y, z'
  21  '-y, -x, z'
  22  '-x+y, -x, z'
  23  '-y, x-y, z'
  24  'x, y, z'
loop_
 _atom_type_symbol
 _atom_type_oxidation_number
  C0+  0
loop_
 _atom_site_label
 _atom_site_type_symbol
 _atom_site_symmetry_multiplicity
 _atom_site_Wyckoff_symbol
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_B_iso_or_equiv
 _atom_site_occupancy
 _atom_site_attached_hydrogens
  C1  C0+  2  b  0  0  0.25  .  1.  0
  C2  C0+  2  c  0.3333  0.6667  0.25  .  1.  0"""
        for l1, l2, l3 in zip(str(c).split("\n"), cif_str.split("\n"),
                              cif_str_2.split("\n")):
            self.assertEqual(l1.strip(), l2.strip())
            self.assertEqual(l2.strip(), l3.strip())