diff --git a/pyproject.toml b/pyproject.toml
index 3ddaa278b..2b9dc55f0 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -66,7 +66,7 @@ all = [
 ]
 dev = [
     "hatch",
-    "ruff>=0.3.0",
+    "ruff>=0.5.1",
     "ipython",
     "pytest",
     "pytest-cov",
diff --git a/tests/utils/test_compiler.py b/tests/utils/test_compiler.py
index 79fc5fed1..0840da4a8 100644
--- a/tests/utils/test_compiler.py
+++ b/tests/utils/test_compiler.py
@@ -8,7 +8,7 @@
     vlc = None
 
 
-@pytest.fixture()
+@pytest.fixture
 def chart():
     return (
         Chart("cars.json")
diff --git a/tests/utils/test_core.py b/tests/utils/test_core.py
index e127885d8..8327d3afe 100644
--- a/tests/utils/test_core.py
+++ b/tests/utils/test_core.py
@@ -249,7 +249,7 @@ def test_update_nested():
     assert output == output2
 
 
-@pytest.fixture()
+@pytest.fixture
 def channels():
     channels = types.ModuleType("channels")
     exec(FAKE_CHANNELS_MODULE, channels.__dict__)
diff --git a/tests/utils/test_html.py b/tests/utils/test_html.py
index faee7b4c8..1ce63445f 100644
--- a/tests/utils/test_html.py
+++ b/tests/utils/test_html.py
@@ -3,7 +3,7 @@
 from altair.utils.html import spec_to_html
 
 
-@pytest.fixture()
+@pytest.fixture
 def spec():
     return {
         "data": {"url": "data.json"},
diff --git a/tests/utils/test_mimebundle.py b/tests/utils/test_mimebundle.py
index a7ab352b0..1d7130f18 100644
--- a/tests/utils/test_mimebundle.py
+++ b/tests/utils/test_mimebundle.py
@@ -15,7 +15,7 @@
     vf = None
 
 
-@pytest.fixture()
+@pytest.fixture
 def vegalite_spec():
     return {
         "$schema": "https://vega.github.io/schema/vega-lite/v5.json",
@@ -41,7 +41,7 @@ def vegalite_spec():
     }
 
 
-@pytest.fixture()
+@pytest.fixture
 def vega_spec():
     return {
         "$schema": "https://vega.github.io/schema/vega/v5.json",
diff --git a/tests/utils/test_schemapi.py b/tests/utils/test_schemapi.py
index 2fafa43a8..b8af99cc3 100644
--- a/tests/utils/test_schemapi.py
+++ b/tests/utils/test_schemapi.py
@@ -288,7 +288,7 @@ def test_schema_validator_selection():
         Draft6Schema.from_dict(dct)
 
 
-@pytest.fixture()
+@pytest.fixture
 def dct():
     return {
         "a": {"foo": "bar"},
diff --git a/tests/vegalite/test_common.py b/tests/vegalite/test_common.py
index ca99e942a..2c043f47f 100644
--- a/tests/vegalite/test_common.py
+++ b/tests/vegalite/test_common.py
@@ -7,7 +7,7 @@
 from altair.vegalite import v5
 
 
-@pytest.fixture()
+@pytest.fixture
 def basic_spec():
     return {
         "data": {"url": "data.csv"},
diff --git a/tests/vegalite/v5/test_api.py b/tests/vegalite/v5/test_api.py
index 556bda631..a7197e0b1 100644
--- a/tests/vegalite/v5/test_api.py
+++ b/tests/vegalite/v5/test_api.py
@@ -64,7 +64,7 @@ def _make_chart_type(chart_type):
         raise ValueError(msg)
 
 
-@pytest.fixture()
+@pytest.fixture
 def basic_chart():
     data = pd.DataFrame(
         {
diff --git a/tests/vegalite/v5/test_data.py b/tests/vegalite/v5/test_data.py
index a2af707fa..5603912f8 100644
--- a/tests/vegalite/v5/test_data.py
+++ b/tests/vegalite/v5/test_data.py
@@ -6,7 +6,7 @@
 from altair.vegalite.v5 import data as alt
 
 
-@pytest.fixture()
+@pytest.fixture
 def sample_data():
     return pd.DataFrame({"x": range(10), "y": range(10)})
 
diff --git a/tests/vegalite/v5/test_renderers.py b/tests/vegalite/v5/test_renderers.py
index a20de1503..b84aa9796 100644
--- a/tests/vegalite/v5/test_renderers.py
+++ b/tests/vegalite/v5/test_renderers.py
@@ -19,7 +19,7 @@
     anywidget = None  # type: ignore
 
 
-@pytest.fixture()
+@pytest.fixture
 def chart():
     return alt.Chart("data.csv").mark_point()
 
diff --git a/tests/vegalite/v5/test_theme.py b/tests/vegalite/v5/test_theme.py
index 64bb9cf28..0eab5546d 100644
--- a/tests/vegalite/v5/test_theme.py
+++ b/tests/vegalite/v5/test_theme.py
@@ -4,7 +4,7 @@
 from altair.vegalite.v5.theme import VEGA_THEMES
 
 
-@pytest.fixture()
+@pytest.fixture
 def chart():
     return alt.Chart("data.csv").mark_bar().encode(x="x:Q")