Convert to list for test clarity

Author: amas0

test/test_runset.py

@@ -331,10 +331,11 @@ def test_metric_output_filename() -> None:
     )
     runset = RunSet(args=cmdstan_args, chains=2)
     assert len(runset.metric_files) == 2
-    assert all(
+    correct_output_files = [
         f.endswith(f"{base_file}_{i}_metric.json")
         for i, f in zip(chain_ids, runset.metric_files)
-    )
+    ]
+    assert all(correct_output_files)
 
     runset = RunSet(args=cmdstan_args, chains=2, one_process_per_chain=False)
     assert len(runset.metric_files) == 2