diff --git a/.github/workflows/run_test.yml b/.github/workflows/run_test.yml
index 54ec0c9..72a0b24 100644
--- a/.github/workflows/run_test.yml
+++ b/.github/workflows/run_test.yml
@@ -7,7 +7,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        python-version: ["3.9", "3.10", "3.11"]
+        python-version: ["3.9", "3.10", "3.11", "3.12"]
 
     steps:
       - uses: actions/checkout@v3
diff --git a/emcfile/_pattern_sone.py b/emcfile/_pattern_sone.py
index 8d1db85..2e28eba 100644
--- a/emcfile/_pattern_sone.py
+++ b/emcfile/_pattern_sone.py
@@ -299,9 +299,7 @@ def check_indices_ordered(self) -> bool:
             return False
         a = np.subtract(self.place_ones[1:], self.place_ones[:-1], dtype=int)
         a[self.ones_idx[1:-1] - 1] = 1
-        if np.any(a <= 0):
-            return False
-        return True
+        return not np.any(a <= 0)
 
     def ensure_indices_ordered(self) -> None:
         if self.check_indices_ordered():
diff --git a/emcfile/tests/test_patterns.py b/emcfile/tests/test_patterns.py
index 2df68c8..fd6a4a7 100644
--- a/emcfile/tests/test_patterns.py
+++ b/emcfile/tests/test_patterns.py
@@ -212,7 +212,7 @@ def test_write_patterns(suffix, data_list):
         logging.info(f"speed[single]: {all_data.nbytes * 1e-9 /t1:.2f} GB/s")
 
         t = time.time()
-        ef.write_patterns(data_list, f0.name, overwrite=True)
+        ef.write_patterns(data_list, f0.name, buffer_size=2**12, overwrite=True)
         t0 = time.time() - t
         logging.info(
             "speed[multiple; #patterns=%d]: %.2f GB/s",