FIX: Fix unit test

Author: adamshephard

tests/test_app_bokeh.py

@@ -286,13 +286,12 @@ def test_add_slide_layer(doc: Document, data_path: pytest.TempPathFactory) -> No
     slide_select.value = [data_path["slide1"].name]
 
     layer_drop = doc.get_model_by_name("layer_drop0")
-    slide_layer_path = str(data_path["overlay_image"])  # e.g. some .png or .jpg
+    slide_layer_path = str(data_path["img_overlay"])  # e.g. some .png or .jpg
 
     click = MenuItemClick(layer_drop, slide_layer_path)
     layer_drop._trigger_event(click)
 
-    # assert a layer was added and tiles changed
-    assert "slide_windows" in doc.models, "Slide windows missing"
+    assert len(layer_drop.menu) == 5
 
 
 def test_tap_query() -> None: