def test_preview_next_byte(self):
file_reader = FileReader(io.StringIO('a'))
preview_char = file_reader.preview_next_char()
char = file_reader.read_char()
self.assertEqual(char, preview_char)
def test_read_byte_when_end_of_file(self):
file_reader = FileReader(io.StringIO(''))
char = file_reader.read_char()
self.assertEqual(char, '')
def test_update_position_with_newline(self):
file_reader = FileReader(io.StringIO("\n"))
file_reader.read_char()
self.assertEqual(file_reader.current_line, 2)
self.assertEqual(file_reader.current_column, 1)
def test_read_byte(self):
file_reader = FileReader(io.StringIO('a'))
char = file_reader.read_char()
self.assertEqual(char, 'a')
