additional test case for pandas-devgh-22783

Author: simonjayhawkins

pandas/tests/io/formats/data/gh22783_named_columns_index.html

@@ -0,0 +1,31 @@
+<table border="1" class="dataframe">
+  <thead>
+    <tr style="text-align: right;">
+      <th>columns.name</th>
+      <th>0</th>
+      <th>1</th>
+      <th>...</th>
+      <th>3</th>
+      <th>4</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <th></th>
+      <td>1.764052</td>
+      <td>0.400157</td>
+      <td>...</td>
+      <td>2.240893</td>
+      <td>1.867558</td>
+    </tr>
+    <tr>
+      <th></th>
+      <td>-0.977278</td>
+      <td>0.950088</td>
+      <td>...</td>
+      <td>-0.103219</td>
+      <td>0.410599</td>
+    </tr>
+  </tbody>
+</table>
+  

pandas/tests/io/formats/test_to_html.py

@@ -494,13 +494,20 @@ def test_to_html_truncation_index_false_max_rows(self, datapath, index):
         assert result == expected
 
     @pytest.mark.parametrize('index', [False, 0])
-    def test_to_html_truncation_index_false_max_cols(self, datapath, index):
+    @pytest.mark.parametrize('col_index_named, expected_output', [
+        (False, 'gh22783_expected_output'),
+        (True, 'gh22783_named_columns_index')
+    ])
+    def test_to_html_truncation_index_false_max_cols(
+            self, datapath, index, col_index_named, expected_output):
         # GH 22783
         data = [[1.764052, 0.400157, 0.978738, 2.240893, 1.867558],
                 [-0.977278, 0.950088, -0.151357, -0.103219, 0.410599]]
         df = DataFrame(data)
+        if col_index_named:
+            df.columns.rename('columns.name', inplace=True)
         result = df.to_html(max_cols=4, index=index)
-        expected = expected_html(datapath, 'gh22783_expected_output')
+        expected = expected_html(datapath, expected_output)
         assert result == expected
 
     def test_to_html_notebook_has_style(self):