test(artifacts): flush writes instead of sleeping to wait on file wri…

…tes (#4523)

test(artifacts): flush writes instead of sleeping

For some reason on my machine the calls to  don't work consistently;
this is faster and more reliable as a way to ensure files are written with
sequential c/m/a times.

tests/unit_tests/test_wandb_artifacts_cache.py

@@ -2,7 +2,6 @@
 import os
 import pathlib
 import random
-import time
 from multiprocessing import Pool
 
 import pytest
@@ -162,18 +161,22 @@ def test_artifacts_cache_cleanup():
     os.makedirs(path_1)
     with open(os.path.join(path_1, "aardvark"), "w") as f:
         f.truncate(5000)
-    time.sleep(0.1)
+        f.flush()
+        os.fsync(f)
 
     path_2 = os.path.join(cache_root, "ab")
     os.makedirs(path_2)
     with open(os.path.join(path_2, "absolute"), "w") as f:
         f.truncate(2000)
-    time.sleep(0.1)
+        f.flush()
+        os.fsync(f)
 
     path_3 = os.path.join(cache_root, "ac")
     os.makedirs(path_3)
     with open(os.path.join(path_3, "accelerate"), "w") as f:
         f.truncate(1000)
+        f.flush()
+        os.fsync(f)
 
     cache = wandb_sdk.wandb_artifacts.ArtifactsCache("cache")
     reclaimed_bytes = cache.cleanup(5000)