test: add tests

src/magicgui/backends/_ipynb/widgets.py

@@ -266,7 +266,7 @@ class _IPySupportsIcon(protocols.SupportsIcon):
 
     _ipywidget: ipywdg.Button
 
-    def _mgui_set_icon(self, value: str, color: str) -> None:
+    def _mgui_set_icon(self, value: str | None, color: str | None) -> None:
         """Set icon."""
         # only ipywdg.Button actually supports icons.
         # but our button protocol allows it for all buttons subclasses
@@ -277,6 +277,7 @@ def _mgui_set_icon(self, value: str, color: str) -> None:
             # which works for iconify icons served by qt, while still
             # allowing for bare "icon-name" syntax which works for ipywidgets.
             # note however... only fa4/5 icons will work for ipywidgets.
+            value = value or ""
             self._ipywidget.icon = value.replace("fa-", "").split(":", 1)[-1]
             self._ipywidget.style.text_color = color
 

src/magicgui/backends/_qtpy/widgets.py

@@ -457,6 +457,11 @@ def _update_icon(self) -> None:
             pal = self._qwidget.palette()
             color = pal.color(QPalette.ColorRole.WindowText).name()
 
+        if ":" not in value:
+            # for parity with the other backends, assume fontawesome
+            # if no prefix is given.
+            value = f"fa-regular:{value}"
+
         try:
             self._qwidget.setIcon(superqt.QIconifyIcon(value, color=color))
         except (OSError, ValueError) as e:

tests/test_widgets.py

@@ -809,6 +809,17 @@ def test_pushbutton_click_signal():
     mock2.assert_called_once()
 
 
+def test_pushbutton_icon(backend: str):
+    use_app(backend)
+    btn = widgets.PushButton(icon="mdi:folder")
+    btn.set_icon("smile", "red")
+    btn.set_icon(None)
+
+    if backend == "qt":
+        with pytest.warns(UserWarning, match="Could not set iconify icon"):
+            btn.set_icon("bad:key")
+
+
 def test_list_edit():
     """Test ListEdit."""
     from typing import List