code: def test_erfinv(self):
      self.check_unary("erfinv")
      self.check_unary_random("erfinv", scale=2, offset=-1)
      self.check_unary_boundary("erfinv", boundary=-1)
      self.check_unary_boundary("erfinv", boundary=1)
  
imports: import unittest
  import numpy
  import cupy
  from cupy import testing
  import cupyx.scipy.special
label_desc: Use image node_id 4 for calling the _TestBase obj's underlying member method code with example usage: obj.test_erfinv() without return types