Add test to agree on desired aligned behavior of ls for empty directo…

…ries.

gcsfs/tests/test_core.py

@@ -163,7 +163,6 @@ def test_pickle(gcs):
     gcs.touch(a)
     assert gcs.ls(TEST_BUCKET) == gcs2.ls(TEST_BUCKET)
 
-
 def test_ls_touch(gcs):
     assert not gcs.exists(TEST_BUCKET + "/tmp/test")
 
@@ -177,6 +176,14 @@ def test_ls_touch(gcs):
     assert {d["name"] for d in L_d} == {a, b}
 
 
+# DO NOT MERGE!
+# Note: We assume this test will fail. Once it does in CI, we will update the code to make it pass.
+# Only then can this PR be approved and merged.
+def test_ls_empty_dir(gcs):
+    gcs.mkdir(TEST_BUCKET + "/test")
+    assert gcs.ls(TEST_BUCKET + "/test", False) == []
+
+
 def test_rm(gcs):
     assert not gcs.exists(a)
     gcs.touch(a)