code: def test_diff_readonly(self):
      # https://github.com/pandas-dev/pandas/issues/35559
      arr = np.random.default_rng(2).standard_normal((5, 2))
      arr.flags.writeable = False
      df = DataFrame(arr)
      result = df.diff()
      expected = DataFrame(np.array(df)).diff()
      tm.assert_frame_equal(result, expected)
  
imports: import numpy
  import pytest
  import pandas
  from pandas import DataFrame, Series, Timestamp, date_range
  import pandas._testing
label_desc: Use image node_id 22 for calling the TestDataFrameDiff obj's underlying member method code with example usage: obj.test_diff_readonly() without return types