TST: use expected_html for to_html tests (pandas-dev#40981)

Author: mzeitlin11

pandas/tests/io/formats/data/html/gh13828_expected_output.html

@@ -0,0 +1,21 @@
+<table border="1" class="dataframe">
+  <thead>
+    <tr style="text-align: right;">
+      <th></th>
+      <th>Group</th>
+      <th>Data</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <th>0</th>
+      <td>A</td>
+      <td>1.22</td>
+    </tr>
+    <tr>
+      <th>1</th>
+      <td>A</td>
+      <td>{na_rep}</td>
+    </tr>
+  </tbody>
+</table>

pandas/tests/io/formats/data/html/gh40024_expected_output.html

@@ -0,0 +1,18 @@
+<table border="1" class="dataframe">
+  <thead>
+    <tr style="text-align: right;">
+      <th></th>
+      <th>x</th>
+    </tr>
+  </thead>
+  <tbody>
+    <tr>
+      <th>0</th>
+      <td>1,000</td>
+    </tr>
+    <tr>
+      <th>1</th>
+      <td>test</td>
+    </tr>
+  </tbody>
+</table>

pandas/tests/io/formats/test_to_html.py

@@ -851,7 +851,7 @@ def test_to_html_multilevel(multiindex_year_month_day_dataframe_random_data):
 
 
 @pytest.mark.parametrize("na_rep", ["NaN", "Ted"])
-def test_to_html_na_rep_and_float_format(na_rep):
+def test_to_html_na_rep_and_float_format(na_rep, datapath):
     # https://github.com/pandas-dev/pandas/issues/13828
     df = DataFrame(
         [
@@ -861,51 +861,14 @@ def test_to_html_na_rep_and_float_format(na_rep):
         columns=["Group", "Data"],
     )
     result = df.to_html(na_rep=na_rep, float_format="{:.2f}".format)
-    expected = f"""<table border="1" class="dataframe">
-  <thead>
-    <tr style="text-align: right;">
-      <th></th>
-      <th>Group</th>
-      <th>Data</th>
-    </tr>
-  </thead>
-  <tbody>
-    <tr>
-      <th>0</th>
-      <td>A</td>
-      <td>1.22</td>
-    </tr>
-    <tr>
-      <th>1</th>
-      <td>A</td>
-      <td>{na_rep}</td>
-    </tr>
-  </tbody>
-</table>"""
+    expected = expected_html(datapath, "gh13828_expected_output")
+    expected = expected.format(na_rep=na_rep)
     assert result == expected
 
 
-def test_to_html_float_format_object_col():
+def test_to_html_float_format_object_col(datapath):
     # GH#40024
     df = DataFrame(data={"x": [1000.0, "test"]})
     result = df.to_html(float_format=lambda x: f"{x:,.0f}")
-    expected = """<table border="1" class="dataframe">
-  <thead>
-    <tr style="text-align: right;">
-      <th></th>
-      <th>x</th>
-    </tr>
-  </thead>
-  <tbody>
-    <tr>
-      <th>0</th>
-      <td>1,000</td>
-    </tr>
-    <tr>
-      <th>1</th>
-      <td>test</td>
-    </tr>
-  </tbody>
-</table>"""
-
+    expected = expected_html(datapath, "gh40024_expected_output")
     assert result == expected