make check_training_data_exists more strict, and test it

cellfinder/napari/curation.py

@@ -495,24 +495,29 @@ def check_image_data_for_extraction(self) -> bool:
             return False
 
     def check_training_data_exists(self) -> bool:
+        """
+        Returns true if both training layers exist, and have len > 0.
+        Otherwise displays useful explanatory info and returns False.
+        """
         if not (
-            self.training_data_cell_layer or self.training_data_non_cell_layer
+            self.training_data_cell_layer and self.training_data_non_cell_layer
         ):
             show_info(
                 "No training data layers have been added. "
-                "Please add a layer and annotate some points.",
+                "Please add layers for both cells and non-cells,"
+                "and annotate some points in both.",
             )
             return False
         else:
             if (
                 len(self.training_data_cell_layer.data) > 0
-                or len(self.training_data_non_cell_layer.data) > 0
+                and len(self.training_data_non_cell_layer.data) > 0
             ):
                 return True
             else:
                 show_info(
                     "No training data points have been added. "
-                    "Please annotate some points.",
+                    "Please annotate points in both training data layers.",
                 )
                 return False
 

tests/napari/test_curation.py

@@ -210,3 +210,26 @@ def test_check_layer_removal_sync(valid_curation_widget):
     assert valid_curation_widget.background_layer is None
     assert valid_curation_widget.training_data_cell_layer is None
     assert valid_curation_widget.training_data_non_cell_layer is None
+
+
+@pytest.mark.xfail(reason="See discussion in #443", raises=AssertionError)
+@pytest.mark.parametrize(
+    "layer_indices_to_remove",
+    [[-2], [-3], [-2, -3]],
+    ids=(
+        "users deletes non-cell training data layer",
+        "user deletes cell training data layer",
+        "user deletes both",
+    ),
+)
+def test_training_data_does_not_exist_when_user_removes_layers(
+    valid_curation_widget, layer_indices_to_remove
+):
+    for layer in layer_indices_to_remove:
+        valid_curation_widget.viewer.layers.pop(layer)
+    assert not valid_curation_widget.check_training_data_exists()
+
+
+@pytest.mark.xfail(reason="See discussion in #443", raises=AssertionError)
+def test_valid_widget_has_valid_training_data(valid_curation_widget):
+    assert valid_curation_widget.check_training_data_exists()