diff --git a/discretisedfield/line.py b/discretisedfield/line.py
index 96803576..2a84c9b1 100644
--- a/discretisedfield/line.py
+++ b/discretisedfield/line.py
@@ -170,7 +170,7 @@ def point_columns(self):
 
     @point_columns.setter
     def point_columns(self, val):
-        if len(val) != 3:
+        if len(val) != len(self._point_columns):
             msg = f"Cannot change column names with a list of lenght {len(val)}."
             raise ValueError(msg)
 
diff --git a/discretisedfield/mesh.py b/discretisedfield/mesh.py
index b06c3b80..95c6bf71 100644
--- a/discretisedfield/mesh.py
+++ b/discretisedfield/mesh.py
@@ -1546,7 +1546,7 @@ def dV(self):
         8.0
 
         """
-        return np.product(self.cell)
+        return np.prod(self.cell)
 
     def scale(self, factor, reference_point=None, inplace=False):
         """Scale the underlying region and all subregions.
diff --git a/discretisedfield/tests/test_interact.py b/discretisedfield/tests/test_interact.py
index 55a883c2..9bea5135 100644
--- a/discretisedfield/tests/test_interact.py
+++ b/discretisedfield/tests/test_interact.py
@@ -11,4 +11,4 @@ def test_interact():
     # Only test whether it runs.
     @df.interact(x=field.mesh.slider("x"))
     def myplot(x):
-        field.plane(x=x).mpl()
+        field.sel(x=x).mpl()
diff --git a/discretisedfield/tools/tools.py b/discretisedfield/tools/tools.py
index 5f9053f3..fc601778 100644
--- a/discretisedfield/tools/tools.py
+++ b/discretisedfield/tools/tools.py
@@ -273,9 +273,17 @@ def topological_charge(field, /, method="continuous", absolute=False):
 
     q = topological_charge_density(field, method=method)
     if absolute:
-        return float(abs(q).integrate())
+        result = abs(q).integrate()
+        if isinstance(result, np.ndarray) and result.size == 1:
+            result = result.item()
+        assert np.isscalar(result), "Expected a scalar result from integration"
+        return float(result)
     else:
-        return float(q.integrate())
+        result = q.integrate()
+        if isinstance(result, np.ndarray) and result.size == 1:
+            result = result.item()
+        assert np.isscalar(result), "Expected a scalar result from integration"
+        return float(result)
 
 
 def emergent_magnetic_field(field):
diff --git a/pytest.ini b/pytest.ini
new file mode 100644
index 00000000..7b497deb
--- /dev/null
+++ b/pytest.ini
@@ -0,0 +1,9 @@
+[pytest]
+python_files = test_*.py
+python_functions = test_*
+filterwarnings =
+    ignore::DeprecationWarning:traitlets.*:
+    #ignore:Automatic coloring is only supported for 3d fields.*:UserWarning
+    ignore:The truth value of an empty array is ambiguous.*:DeprecationWarning
+    ignore:invalid value encountered in divide:RuntimeWarning
+    ignore:`ipykernel.pylab.backend_inline` is deprecated.*:DeprecationWarning