TST: add test to io/formats/test_to_html.py to close GH6131 (#22588)

Author: simonjayhawkins

pandas/tests/io/formats/test_to_html.py

@@ -1844,6 +1844,67 @@ def test_to_html_no_index_max_rows(self):
  </table>""")
  assert result == expected
 
+ def test_to_html_multiindex_max_cols(self):
+ # GH 6131
+ index = MultiIndex(levels=[['ba', 'bb', 'bc'], ['ca', 'cb', 'cc']],
+ labels=[[0, 1, 2], [0, 1, 2]],
+ names=['b', 'c'])
+ columns = MultiIndex(levels=[['d'], ['aa', 'ab', 'ac']],
+ labels=[[0, 0, 0], [0, 1, 2]],
+ names=[None, 'a'])
+ data = np.array(
+ [[1., np.nan, np.nan], [np.nan, 2., np.nan], [np.nan, np.nan, 3.]])
+ df = DataFrame(data, index, columns)
+ result = df.to_html(max_cols=2)
+ expected = dedent("""\
+ <table border="1" class="dataframe">
+ <thead>
+ <tr>
+ <th></th>
+ <th></th>
+ <th colspan="3" halign="left">d</th>
+ </tr>
+ <tr>
+ <th></th>
+ <th>a</th>
+ <th>aa</th>
+ <th>...</th>
+ <th>ac</th>
+ </tr>
+ <tr>
+ <th>b</th>
+ <th>c</th>
+ <th></th>
+ <th></th>
+ <th></th>
+ </tr>
+ </thead>
+ <tbody>
+ <tr>
+ <th>ba</th>
+ <th>ca</th>
+ <td>1.0</td>
+ <td>...</td>
+ <td>NaN</td>
+ </tr>
+ <tr>
+ <th>bb</th>
+ <th>cb</th>
+ <td>NaN</td>
+ <td>...</td>
+ <td>NaN</td>
+ </tr>
+ <tr>
+ <th>bc</th>
+ <th>cc</th>
+ <td>NaN</td>
+ <td>...</td>
+ <td>3.0</td>
+ </tr>
+ </tbody>
+ </table>""")
+ assert result == expected
+
  def test_to_html_notebook_has_style(self):
  df = pd.DataFrame({"A": [1, 2, 3]})
  result = df.to_html(notebook=True)