TST: Add test for default line_terminator argument

Author: BenRussert

pandas/tests/io/formats/test_to_csv.py

@@ -3,6 +3,7 @@
 import sys
 
 import pytest
+from unittest.mock import patch
 
 import os
 import numpy as np
@@ -563,3 +564,20 @@ def test_to_csv_compression(self, compression_only,
             result = pd.read_csv(path, index_col=0,
                                  compression=read_compression)
             tm.assert_frame_equal(result, df)
+
+
+def test_csv_formatter_line_terminator_default():
+    # see GH #23608
+    # ensure default line_terminator is os.linesep
+    df = tm.makeDataFrame()
+
+    # fake default os.linesep to look like windows
+    with patch.object(os, 'linesep', '\r\n'):
+        # Import in this context so it uses the patched os.linesep
+        from pandas.io.formats.csvs import CSVFormatter
+
+        formatter_with_argument = CSVFormatter(df, line_terminator='\r')
+        assert formatter_with_argument.line_terminator == '\r'
+
+        formatter = CSVFormatter(df)
+        assert formatter.line_terminator == os.linesep