new setter and test

festim/settings.py

@@ -1,3 +1,6 @@
+import festim as F
+
+
 class Settings:
     """Settings for a festim simulation.
 
@@ -33,3 +36,18 @@ def __init__(
         self.max_iterations = max_iterations
         self.final_time = final_time
         self.stepsize = stepsize
+
+    @property
+    def stepsize(self):
+        return self._stepsize
+
+    @stepsize.setter
+    def stepsize(self, value):
+        if value is None:
+            self._stepsize = None
+        elif isinstance(value, (float, int)):
+            self._stepsize = F.Stepsize(initial_value=value)
+        elif isinstance(value, F.Stepsize):
+            self._stepsize = value
+        else:
+            raise TypeError("stepsize must be an of type int, float or festim.Stepsize")

test/test_settings.py

@@ -0,0 +1,21 @@
+import festim as F
+import numpy as np
+import pytest
+
+
+@pytest.mark.parametrize("value", [1, F.Stepsize(initial_value=23.0), 1.0, "coucou"])
+def test_stepsize_value(value):
+    """Test that the stepsize is correctly set"""
+    my_model = F.HydrogenTransportProblem()
+    my_model.settings = F.Settings(atol=1, rtol=0.1)
+
+    if isinstance(value, (int, float)):
+        my_model.settings.stepsize = value
+        assert isinstance(my_model.settings.stepsize, F.Stepsize)
+        assert np.isclose(my_model.settings.stepsize.initial_value, value)
+    elif isinstance(value, F.Stepsize):
+        my_model.settings.stepsize = value
+        assert np.isclose(my_model.settings.stepsize.initial_value, 23)
+    else:
+        with pytest.raises(TypeError):
+            my_model.settings.stepsize = value