Add test for Parquet GCS write

Author: bnaul

pandas/tests/io/test_gcs.py

@@ -1,3 +1,5 @@
+import os
+from contextlib import contextmanager
 from io import StringIO
 
 import numpy as np
@@ -60,6 +62,31 @@ def open(*args):
     assert_frame_equal(df1, df2)
 
 
+@td.skip_if_no("gcsfs")
+def test_to_parquet_gcs_new_file(monkeypatch, tmpdir):
+    """Regression test for writing to a not-yet-existent GCS Parquet file."""
+    df1 = DataFrame(
+        {
+            "int": [1, 3],
+            "float": [2.0, np.nan],
+            "str": ["t", "s"],
+            "dt": date_range("2018-06-18", periods=2),
+        }
+    )
+
+    class MockGCSFileSystem:
+        @contextmanager
+        def open(self, path, mode='r', *args):
+            if 'w' not in mode:
+                raise FileNotFoundError
+            with open(os.path.join(tmpdir, 'test.parquet'), mode) as f:
+                yield f
+
+    monkeypatch.setattr("gcsfs.GCSFileSystem", MockGCSFileSystem)
+    df1.to_parquet("gs://test/test.csv", index=True, engine='fastparquet',
+                   compression=None)
+
+
 @td.skip_if_no("gcsfs")
 def test_gcs_get_filepath_or_buffer(monkeypatch):
     df1 = DataFrame(