diff --git a/tests/unit/conftest.py b/tests/unit/conftest.py
index 4119e99..dde307b 100644
--- a/tests/unit/conftest.py
+++ b/tests/unit/conftest.py
@@ -1,13 +1,13 @@
 from unittest.mock import AsyncMock, MagicMock
 
-from pytest import fixture
+import pytest
 
 
-@fixture
+@pytest.fixture
 def reader_double():
     """Factory of OPC reader doubles holding subscriptions for the given slots.
 
-    Like the real readers (ServerReader, OpcManager), `subscriptions` is keyed by slot
+    Like the real ServerReader, `subscriptions` is keyed by slot
     and `unsubscribe` drops the slot from it.
     """
 
diff --git a/tests/unit/connection/test_certs.py b/tests/unit/connection/test_certs.py
index 84a686a..9f392a3 100644
--- a/tests/unit/connection/test_certs.py
+++ b/tests/unit/connection/test_certs.py
@@ -46,7 +46,8 @@ async def test_local_files_keep_the_object_extension(tmp_path):
 
     cert, key = await provider.fetch(certificate(ext='der'))
 
-    assert cert.endswith('cert.der') and key.endswith('key.der')
+    assert cert.endswith('cert.der')
+    assert key.endswith('key.der')
 
 
 @pytest.mark.asyncio
@@ -61,9 +62,10 @@ async def test_local_files_keep_the_object_extension(tmp_path):
 )
 async def test_fetch_of_an_incomplete_certificate_raises_clear_error(tmp_path, broken):
     provider, minio = _provider(tmp_path)
+    incomplete = {**certificate(), **broken}
 
     with pytest.raises(CertificateNotConfiguredError, match='opc_certificates|certificate_id'):
-        await provider.fetch({**certificate(), **broken})
+        await provider.fetch(incomplete)
     minio.download_file.assert_not_awaited()
 
 
diff --git a/tests/unit/connection/test_clock.py b/tests/unit/connection/test_clock.py
index f947d86..30f60cf 100644
--- a/tests/unit/connection/test_clock.py
+++ b/tests/unit/connection/test_clock.py
@@ -5,4 +5,6 @@ def test_elapsed_is_non_negative_and_monotonic():
     clk = MonotonicClock()
     a = clk.elapsed()
     b = clk.elapsed()
-    assert a >= 0 and b >= a  # never negative even if wall clock jumps back
+    # never negative even if wall clock jumps back
+    assert a >= 0
+    assert b >= a
diff --git a/tests/unit/engines/test_write.py b/tests/unit/engines/test_write.py
index d595d67..2d2aded 100644
--- a/tests/unit/engines/test_write.py
+++ b/tests/unit/engines/test_write.py
@@ -346,8 +346,10 @@ async def test_write_error_logs_the_reason_and_sets_the_model_status():
     await eng.write(base_cmd())
 
     logged = eng.logger.error.call_args.args[0]
-    assert 'RuntimeError' in logged and 'BadWriteNotSupported' in logged
-    assert 'addr=ns=2;i=5' in logged and 'model_id=m1' in logged
+    assert 'RuntimeError' in logged
+    assert 'BadWriteNotSupported' in logged
+    assert 'addr=ns=2;i=5' in logged
+    assert 'model_id=m1' in logged
     status_call = next(
         c
         for c in eng.emit_metric.await_args_list
diff --git a/tests/unit/io/test_data_sink_status.py b/tests/unit/io/test_data_sink_status.py
index 590796a..01324ca 100644
--- a/tests/unit/io/test_data_sink_status.py
+++ b/tests/unit/io/test_data_sink_status.py
@@ -58,7 +58,8 @@ async def test_update_write_status_targets_model_row_with_precedence():
     assert sql.startswith('UPDATE sientia_data.pred_m1 SET write_status=')
     assert 'CASE sientia_data.pred_m1.write_status WHEN' in sql
     # values must be bound params, never interpolated into the SQL text itself
-    assert '2026-07-13T00:00:00Z' not in sql and "'ok'" not in sql
+    assert '2026-07-13T00:00:00Z' not in sql
+    assert "'ok'" not in sql
     assert compiled.params['write_status'] == 'ok'
     assert '2026-07-13T00:00:00Z' in compiled.params.values()
     assert _outcome_metric(sink) == 'updated'