TST: Verify functioning of histtype argument (GH23992) (#37063)

* TST: Verify functioning of histtype argument (GH23992)

* Generalize checks and store in common.py

* Update _check_filling function

* Add type hinting

* Update Axis reference to be in line with plotting/_matplotlib/tools.py

* Add conditional import of matplotlib

* Remove type hinting from tests

* Rename function as requested

Author: avinashpancham

pandas/tests/plotting/common.py

@@ -1,4 +1,5 @@
 import os
+from typing import TYPE_CHECKING, Sequence, Union
 import warnings
 
 import numpy as np
@@ -12,6 +13,9 @@
 from pandas import DataFrame, Series, to_datetime
 import pandas._testing as tm
 
+if TYPE_CHECKING:
+    from matplotlib.axes import Axes
+
 
 @td.skip_if_no_mpl
 class TestPlotBase:
@@ -172,6 +176,24 @@ def _check_visible(self, collections, visible=True):
         for patch in collections:
             assert patch.get_visible() == visible
 
+    def _check_patches_all_filled(
+        self, axes: Union["Axes", Sequence["Axes"]], filled: bool = True
+    ) -> None:
+        """
+        Check for each artist whether it is filled or not
+
+        Parameters
+        ----------
+        axes : matplotlib Axes object, or its list-like
+        filled : bool
+            expected filling
+        """
+
+        axes = self._flatten_visible(axes)
+        for ax in axes:
+            for patch in ax.patches:
+                assert patch.fill == filled
+
     def _get_colors_mapped(self, series, colors):
         unique = series.unique()
         # unique and colors length can be differed

pandas/tests/plotting/test_hist_method.py

@@ -128,6 +128,21 @@ def test_plot_fails_when_ax_differs_from_figure(self):
         with pytest.raises(AssertionError):
             self.ts.hist(ax=ax1, figure=fig2)
 
+    @pytest.mark.parametrize(
+        "histtype, expected",
+        [
+            ("bar", True),
+            ("barstacked", True),
+            ("step", False),
+            ("stepfilled", True),
+        ],
+    )
+    def test_histtype_argument(self, histtype, expected):
+        # GH23992 Verify functioning of histtype argument
+        ser = Series(np.random.randint(1, 10))
+        ax = ser.hist(histtype=histtype)
+        self._check_patches_all_filled(ax, filled=expected)
+
     @pytest.mark.parametrize(
         "by, expected_axes_num, expected_layout", [(None, 1, (1, 1)), ("b", 2, (1, 2))]
     )
@@ -364,6 +379,21 @@ def test_hist_column_order_unchanged(self, column, expected):
 
         assert result == expected
 
+    @pytest.mark.parametrize(
+        "histtype, expected",
+        [
+            ("bar", True),
+            ("barstacked", True),
+            ("step", False),
+            ("stepfilled", True),
+        ],
+    )
+    def test_histtype_argument(self, histtype, expected):
+        # GH23992 Verify functioning of histtype argument
+        df = DataFrame(np.random.randint(1, 10, size=(100, 2)), columns=["a", "b"])
+        ax = df.hist(histtype=histtype)
+        self._check_patches_all_filled(ax, filled=expected)
+
     @pytest.mark.parametrize("by", [None, "c"])
     @pytest.mark.parametrize("column", [None, "b"])
     def test_hist_with_legend(self, by, column):
@@ -594,3 +624,18 @@ def test_axis_share_xy(self):
 
         assert ax1._shared_y_axes.joined(ax1, ax2)
         assert ax2._shared_y_axes.joined(ax1, ax2)
+
+    @pytest.mark.parametrize(
+        "histtype, expected",
+        [
+            ("bar", True),
+            ("barstacked", True),
+            ("step", False),
+            ("stepfilled", True),
+        ],
+    )
+    def test_histtype_argument(self, histtype, expected):
+        # GH23992 Verify functioning of histtype argument
+        df = DataFrame(np.random.randint(1, 10, size=(100, 2)), columns=["a", "b"])
+        ax = df.hist(by="a", histtype=histtype)
+        self._check_patches_all_filled(ax, filled=expected)