Add tests/more tests to widgets with low coverage (napari#5864)

# Description

* [x] Add more tests for `QColorSwatch` related widgets
* [x] Add test for `QtToolTipLabel`
* [x] Add test for `QtPluginSorter`

## Notes

While checking the addition of new tests to widgets using the [code
coverage as
guidance](https://app.codecov.io/gh/napari/napari/tree/main/napari/_qt/widgets),
seems like a widget which doesn't have coverage at all exist:
`QtDictTable`. But more interestingly, seems like this widget is not
used anymore? I was unable to find a place inside napari source code
where this widget is used. Maybe it should be removed or moved to an
upstream project like `superqt`?

napari/_qt/widgets/_tests/test_qt_color_swatch.py

@@ -1,8 +1,11 @@
 import numpy as np
 import pytest
+from qtpy.QtCore import Qt
+from qtpy.QtWidgets import QApplication
 
 from napari._qt.widgets.qt_color_swatch import (
     TRANSPARENT,
+    QColorPopup,
     QColorSwatch,
     QColorSwatchEdit,
 )
@@ -17,9 +20,18 @@ def test_succesfull_create_qcolorswatchedit(qtbot, color, tooltip):
     test_color = color or TRANSPARENT
     test_tooltip = tooltip or 'click to set color'
 
+    # check widget creation and base values
     assert widget.color_swatch.toolTip() == test_tooltip
     np.testing.assert_array_equal(widget.color, test_color)
 
+    # check widget popup
+    qtbot.mouseRelease(widget.color_swatch, Qt.MouseButton.LeftButton)
+    color_popup = None
+    for widget in QApplication.topLevelWidgets():
+        if isinstance(widget, QColorPopup):
+            color_popup = widget
+    assert color_popup
+
 
 @pytest.mark.parametrize('color', [None, [1, 1, 1, 1]])
 @pytest.mark.parametrize('tooltip', [None, 'This is a test'])
@@ -30,5 +42,14 @@ def test_succesfull_create_qcolorswatch(qtbot, color, tooltip):
     test_color = color or TRANSPARENT
     test_tooltip = tooltip or 'click to set color'
 
+    # check widget creation and base values
     assert widget.toolTip() == test_tooltip
     np.testing.assert_array_equal(widget.color, test_color)
+
+    # check widget popup
+    qtbot.mouseRelease(widget, Qt.MouseButton.LeftButton)
+    color_popup = None
+    for widget in QApplication.topLevelWidgets():
+        if isinstance(widget, QColorPopup):
+            color_popup = widget
+    assert color_popup

napari/_qt/widgets/_tests/test_qt_plugin_sorter.py

@@ -0,0 +1,147 @@
+import pytest
+
+from napari._qt.widgets.qt_plugin_sorter import QtPluginSorter, rst2html
+
+
+@pytest.mark.parametrize(
+    'text,expected_text',
+    [
+        ("", ""),
+        (
+            """Return a function capable of loading ``path`` into napari, or ``None``.
+
+    This is the primary "**reader plugin**" function.  It accepts a path or
+    list of paths, and returns a list of data to be added to the ``Viewer``.
+    The function may return ``[(None, )]`` to indicate that the file was read
+    successfully, but did not contain any data.
+
+    The main place this hook is used is in :func:`Viewer.open()
+    <napari.components.viewer_model.ViewerModel.open>`, via the
+    :func:`~napari.plugins.io.read_data_with_plugins` function.
+
+    It will also be called on ``File -> Open...`` or when a user drops a file
+    or folder onto the viewer. This function must execute **quickly**, and
+    should return ``None`` if the filepath is of an unrecognized format for
+    this reader plugin.  If ``path`` is determined to be recognized format,
+    this function should return a *new* function that accepts the same filepath
+    (or list of paths), and returns a list of ``LayerData`` tuples, where each
+    tuple is a 1-, 2-, or 3-tuple of ``(data,)``, ``(data, meta)``, or ``(data,
+    meta, layer_type)``.
+
+    ``napari`` will then use each tuple in the returned list to generate a new
+    layer in the viewer using the :func:`Viewer._add_layer_from_data()
+    <napari.components.viewer_model.ViewerModel._add_layer_from_data>`
+    method.  The first, (optional) second, and (optional) third items in each
+    tuple in the returned layer_data list, therefore correspond to the
+    ``data``, ``meta``, and ``layer_type`` arguments of the
+    :func:`Viewer._add_layer_from_data()
+    <napari.components.viewer_model.ViewerModel._add_layer_from_data>`
+    method, respectively.
+
+    .. important::
+
+       ``path`` may be either a ``str`` or a ``list`` of ``str``.  If a
+       ``list``, then each path in the list can be assumed to be one part of a
+       larger multi-dimensional stack (for instance: a list of 2D image files
+       that should be stacked along a third axis). Implementations should do
+       their own checking for ``list`` or ``str``, and handle each case as
+       desired.""",
+            'Return a function capable of loading <code>path</code> into napari, or <code>None</code>.<br><br>    '
+            'This is the primary "<strong>reader plugin</strong>" function.  It accepts a path or<br>    '
+            'list of paths, and returns a list of data to be added to the <code>Viewer</code>.<br>    '
+            'The function may return <code>[(None, )]</code> to indicate that the file was read<br>    '
+            'successfully, but did not contain any data.<br><br>    '
+            'The main place this hook is used is in <code>Viewer.open()</code>, via the<br>    '
+            '<code>read_data_with_plugins</code> function.<br><br>    '
+            'It will also be called on <code>File -> Open...</code> or when a user drops a file<br>    '
+            'or folder onto the viewer. This function must execute <strong>quickly</strong>, and<br>    '
+            'should return <code>None</code> if the filepath is of an unrecognized format for<br>    '
+            'this reader plugin.  If <code>path</code> is determined to be recognized format,<br>    '
+            'this function should return a <em>new</em> function that accepts the same filepath<br>    '
+            '(or list of paths), and returns a list of <code>LayerData</code> tuples, where each<br>    '
+            'tuple is a 1-, 2-, or 3-tuple of <code>(data,)</code>, <code>(data, meta)</code>, or <code>(data,<br>    '
+            'meta, layer_type)</code>.<br><br>    <code>napari</code> will then use each tuple in the returned list to generate a new<br>    '
+            'layer in the viewer using the <code>Viewer._add_layer_from_data()</code><br>    '
+            'method.  The first, (optional) second, and (optional) third items in each<br>    '
+            'tuple in the returned layer_data list, therefore correspond to the<br>    '
+            '<code>data</code>, <code>meta</code>, and <code>layer_type</code> arguments of the<br>    '
+            '<code>Viewer._add_layer_from_data()</code><br>    method, respectively.<br><br>    .. important::<br><br>'
+            '       <code>path</code> may be either a <code>str</code> or a <code>list</code> of <code>str</code>.  If a<br>'
+            '       <code>list</code>, then each path in the list can be assumed to be one part of a<br>       '
+            'larger multi-dimensional stack (for instance: a list of 2D image files<br>       '
+            'that should be stacked along a third axis). Implementations should do<br>       '
+            'their own checking for <code>list</code> or <code>str</code>, and handle each case as<br>       '
+            'desired.',
+        ),
+    ],
+)
+def test_rst2html(text, expected_text):
+    assert rst2html(text) == expected_text
+
+
+def test_create_qt_plugin_sorter(qtbot):
+    plugin_sorter = QtPluginSorter()
+    qtbot.addWidget(plugin_sorter)
+
+    # Check initial hook combobox items
+    hook_combo_box = plugin_sorter.hook_combo_box
+    combobox_items = [
+        hook_combo_box.itemText(idx) for idx in range(hook_combo_box.count())
+    ]
+    assert combobox_items == [
+        'select hook... ',
+        'get_reader',
+        'get_writer',
+        'write_image',
+        'write_labels',
+        'write_points',
+        'write_shapes',
+        'write_surface',
+        'write_vectors',
+    ]
+
+
+@pytest.mark.parametrize(
+    "hook_name,help_info",
+    [
+        ('select hook... ', ''),
+        (
+            'get_reader',
+            'This is the primary "<strong>reader plugin</strong>" function.  It accepts a path or<br>    list of paths, and returns a list of data to be added to the <code>Viewer</code>.<br>',
+        ),
+        (
+            'get_writer',
+            'This function will be called whenever the user attempts to save multiple<br>    layers (e.g. via <code>File -> Save Layers</code>, or<br>    <code>save_layers</code>).<br>',
+        ),
+        (
+            'write_labels',
+            'It is the responsibility of the implementation to check any extension on<br>    <code>path</code> and return <code>None</code> if it is an unsupported extension.',
+        ),
+        (
+            'write_points',
+            'It is the responsibility of the implementation to check any extension on<br>    <code>path</code> and return <code>None</code> if it is an unsupported extension.',
+        ),
+        (
+            'write_shapes',
+            'It is the responsibility of the implementation to check any extension on<br>    <code>path</code> and return <code>None</code> if it is an unsupported extension.',
+        ),
+        (
+            'write_surface',
+            'It is the responsibility of the implementation to check any extension on<br>    <code>path</code> and return <code>None</code> if it is an unsupported extension.',
+        ),
+        (
+            'write_vectors',
+            'It is the responsibility of the implementation to check any extension on<br>    <code>path</code> and return <code>None</code> if it is an unsupported extension.',
+        ),
+    ],
+)
+def test_qt_plugin_sorter_help_info(qtbot, hook_name, help_info):
+    plugin_sorter = QtPluginSorter()
+    qtbot.addWidget(plugin_sorter)
+
+    # Check hook combobox items help tooltip in the info widget
+    info_widget = plugin_sorter.info
+    hook_combo_box = plugin_sorter.hook_combo_box
+    hook_combo_box.setCurrentText(hook_name)
+
+    assert help_info in info_widget.toolTip()

napari/_qt/widgets/_tests/test_qt_tooltip.py

@@ -0,0 +1,23 @@
+import sys
+
+import pytest
+from qtpy.QtWidgets import QToolTip
+
+from napari._qt.widgets.qt_tooltip import QtToolTipLabel
+
+
+@pytest.mark.skipif(
+    sys.platform.startswith('linux') or sys.platform == 'darwin',
+    reason='Timeouts when running on CI with Linux or macOS',
+)
+def test_qt_tooltip_label(qtbot):
+    tooltip_text = "Test QtToolTipLabel showing a tooltip"
+    widget = QtToolTipLabel("Label with a tooltip")
+    widget.setToolTip(tooltip_text)
+    qtbot.addWidget(widget)
+    widget.show()
+
+    assert QToolTip.text() == ""
+    qtbot.mouseMove(widget)
+    qtbot.waitUntil(lambda: QToolTip.isVisible())
+    qtbot.waitUntil(lambda: QToolTip.text() == tooltip_text)