test: is the leading slash breaking Windows tests? (#1178)

* test: is the leading slash breaking Windows tests?

* use a backslash for Windows, forward slash for Linux & MacOS

* give up on any kind of leading slash for Windows

tests/test_0692_fsspec_writing.py

@@ -4,11 +4,14 @@
 import uproot
 import uproot.source.fsspec
 
+import sys
 import os
 import pathlib
 import fsspec
 import numpy as np
 
+is_windows = sys.platform.startswith("win")
+
 
 def test_fsspec_writing_no_integration(tmp_path):
     uri = os.path.join(tmp_path, "some", "path", "file.root")
@@ -46,7 +49,7 @@ def test_fsspec_writing_local(tmp_path, scheme):
 )
 @pytest.mark.parametrize(
     "slash_prefix",
-    ["", "/"],
+    [""] if is_windows else ["", "/"],
 )
 def test_fsspec_writing_local_uri(tmp_path, scheme, slash_prefix, filename):
     uri = scheme + slash_prefix + os.path.join(tmp_path, "some", "path", filename)