code: def test_base64invalid(self):
      # Test base64 with random invalid characters sprinkled throughout
      # (This requires a new version of binascii.)
      MAX_BASE64 = 57
      lines = []
      for i in range(0, len(self.data), MAX_BASE64):
          b = self.type2test(self.rawdata[i : i + MAX_BASE64])
          a = binascii.b2a_base64(b)
          lines.append(a)
  
      fillers = bytearray()
      valid = b"abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789+/"
      for i in range(256):
          if i not in valid:
              fillers.append(i)
  
      def addnoise(line):
          noise = fillers
          ratio = len(line) // len(noise)
          res = bytearray()
          while line and noise:
              if len(line) // len(noise) > ratio:
                  c, line = line[0], line[1:]
              else:
                  c, noise = noise[0], noise[1:]
              res.append(c)
          return res + noise + line
  
      res = bytearray()
      for line in map(addnoise, lines):
          a = self.type2test(line)
          b = binascii.a2b_base64(a)
          res += b
      self.assertEqual(res, self.rawdata)
  
      # Test base64 with just invalid characters, which should return
      # empty strings. TBD: shouldn't it raise an exception instead ?
      self.assertEqual(
          binascii.a2b_base64(self.type2test(fillers)), b""
      )
  
imports: import unittest
  import binascii
  import array
  import re
  from test.support import bigmemtest, _1G, _4G
  from test.support.hypothesis_helper import hypothesis
label_desc: Use image node_id 7 for calling the BinASCIITest obj's underlying member method code with example usage: obj.test_base64invalid() and returns: unknown