fix: ensure multiproc dir is created

Signed-off-by: Aaron Pham <29749331+aarnphm@users.noreply.github.com>

tests/unit/test_metrics.py

@@ -1,9 +1,14 @@
 from __future__ import annotations
 
+from typing import TYPE_CHECKING
+
 import bentoml
 from bentoml._internal.configuration.containers import BentoMLContainer
 from bentoml._internal.server.metrics.prometheus import PrometheusClient
 
+if TYPE_CHECKING:
+    from _pytest.tmpdir import TempPathFactory
+
 
 def test_metrics_initialization():
     o = bentoml.metrics.Gauge(name="test_metrics", documentation="test")
@@ -16,8 +21,8 @@ def test_metrics_initialization():
     assert isinstance(o, bentoml.metrics._LazyMetric)
 
 
-def test_metrics_type():
-    client = PrometheusClient()
+def test_metrics_type(tmp_path_factory: TempPathFactory):
+    client = PrometheusClient(multiproc_dir=str(tmp_path_factory.mktemp("metrics")))
     with BentoMLContainer.metrics_client.patch(client):
         o = bentoml.metrics.Counter(name="test_metrics", documentation="test")
         assert o._attr == "Counter"