Add test for size API (#196)

Author: yanghua

tosfs/tests/test_fsspec.py

@@ -875,3 +875,14 @@ def test_tail(fsspecfs: Any, bucket: str, temporary_workspace: str):
 
     with pytest.raises(IsADirectoryError):
         fsspecfs.tail(path, 3)
+
+
+def test_size(fsspecfs: Any, bucket: str, temporary_workspace: str):
+    file_name = random_str()
+    path = f"{bucket}/{temporary_workspace}/{file_name}"
+    content = "hello world"
+    with fsspecfs.open(path, "w") as f:
+        f.write(content)
+
+    assert fsspecfs.size(path) == len(content)
+    assert fsspecfs.size(f"{bucket}/{temporary_workspace}") == 0