Add test for ShapeFactory plotting method used in the docs.

tests/shapes/test_factory.py

@@ -18,3 +18,21 @@ def test_generate_shape_error(self, shape_factory):
         """Test the generate_shape() method on a non-existent shape."""
         with pytest.raises(ValueError, match='No such shape'):
             _ = shape_factory.generate_shape('does not exist')
+
+    @pytest.mark.parametrize('subset', [4, 5, 8, 10, None])
+    def test_plot_available_shapes(self, shape_factory, monkeypatch, subset):
+        """Test the plot_available_shapes() method."""
+        if subset:
+            monkeypatch.setattr(
+                shape_factory,
+                'AVAILABLE_SHAPES',
+                shape_factory.AVAILABLE_SHAPES[:subset],
+            )
+
+        axs = shape_factory.plot_available_shapes()
+        populated_axs = [ax for ax in axs.flatten() if ax.get_figure()]
+        assert len(populated_axs) == len(shape_factory.AVAILABLE_SHAPES)
+        assert all([ax.get_xlabel() == ax.get_ylabel() == '' for ax in populated_axs])
+        assert set(ax.get_title() for ax in populated_axs) == set(
+            shape_factory.AVAILABLE_SHAPES
+        )