diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
index fea961a201ee..acc365d765d9 100644
--- a/lib/matplotlib/tests/test_axes.py
+++ b/lib/matplotlib/tests/test_axes.py
@@ -6079,7 +6079,8 @@ def invert(x):
 
         secax(0.2, functions=(invert, invert))
         secax(0.4, functions=(lambda x: 2 * x, lambda x: x / 2))
-        secax(0.6, functions=(lambda x: x**2, lambda x: x**(1/2)))
+        with pytest.warns(RuntimeWarning):  # Needs to be fixed.
+            secax(0.6, functions=(lambda x: x**2, lambda x: x**(1/2)))
         secax(0.8)
 
 
@@ -6101,7 +6102,8 @@ def invert(x):
         with np.errstate(divide='ignore'):
             return 1 / x
 
-    ax.secondary_xaxis('top', functions=(invert, invert))
+    with pytest.warns(RuntimeWarning):  # May need to be fixed.
+        ax.secondary_xaxis('top', functions=(invert, invert))
     fig.canvas.draw()
     fig.set_size_inches((7, 4))
     assert_allclose(ax.get_position().extents, [0.125, 0.1, 0.9, 0.9])
diff --git a/lib/matplotlib/tests/test_cbook.py b/lib/matplotlib/tests/test_cbook.py
index 9d35b34c04b3..4dee3018760b 100644
--- a/lib/matplotlib/tests/test_cbook.py
+++ b/lib/matplotlib/tests/test_cbook.py
@@ -353,10 +353,8 @@ def test_normalize_kwargs_pass(inp, expected, kwargs_to_norm):
 def test_warn_external_frame_embedded_python():
     with patch.object(cbook, "sys") as mock_sys:
         mock_sys._getframe = Mock(return_value=None)
-        with warnings.catch_warnings(record=True) as w:
+        with pytest.warns(UserWarning, match=r"\Adummy\Z"):
             cbook._warn_external("dummy")
-    assert len(w) == 1
-    assert str(w[0].message) == "dummy"
 
 
 def test_to_prestep():
diff --git a/lib/mpl_toolkits/axisartist/grid_helper_curvelinear.py b/lib/mpl_toolkits/axisartist/grid_helper_curvelinear.py
index b0cd571def80..2af218781300 100644
--- a/lib/mpl_toolkits/axisartist/grid_helper_curvelinear.py
+++ b/lib/mpl_toolkits/axisartist/grid_helper_curvelinear.py
@@ -121,12 +121,12 @@ def update_lim(self, axes):
                   grid_finder.grid_locator2(lat_min, lat_max)
 
         if self.nth_coord == 0:
-            xx0 = np.full(self._line_num_points, self.value)
+            xx0 = np.full(self._line_num_points, self.value, type(self.value))
             yy0 = np.linspace(lat_min, lat_max, self._line_num_points)
             xx, yy = grid_finder.transform_xy(xx0, yy0)
         elif self.nth_coord == 1:
             xx0 = np.linspace(lon_min, lon_max, self._line_num_points)
-            yy0 = np.full(self._line_num_points, self.value)
+            yy0 = np.full(self._line_num_points, self.value, type(self.value))
             xx, yy = grid_finder.transform_xy(xx0, yy0)
 
         self.grid_info = {
diff --git a/pytest.ini b/pytest.ini
index 730bea97604e..117bd5517b19 100644
--- a/pytest.ini
+++ b/pytest.ini
@@ -7,3 +7,6 @@ python_files = test_*.py
 markers =
     backend: Set alternate Matplotlib backend temporarily.
     style: Set alternate Matplotlib style temporarily.
+
+filterwarnings =
+    error