TST: test to_csv infers compression by default

Author: dhimmel

pandas/tests/io/formats/test_to_csv.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+import gzip
 import sys
 
 import pytest
@@ -351,3 +352,15 @@ 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_compression_defaults_to_infer(tmpdir):
+        """
+        Test that to_csv defaults to inferring compression from paths.
+        https://github.com/pandas-dev/pandas/pull/22011
+        """
+        df = DataFrame({"A": [1]})
+        with tm.ensure_clean('compressed.csv.gz') as path:
+            df.to_csv(path, index=False)
+            with gzip.open(path, 'rt') as read_file:
+                lines = read_file.read().splitlines()
+        assert lines == ['A', '1']