test: improve failure message for tree construction

flavorjones · flavorjones · commit b5ef1ef37b72 · 2023-05-03T08:48:52.000-04:00
where before we saw:

    TestHtml5TreeConstructionWebkit02#test_31 [/home/flavorjones/code/oss/nokogiri/test/html5/test_tree_construction.rb:35]
    Minitest::Assertion: Element &lt;select&gt;&lt;option&gt;&lt;hr&gt;&lt;/option&gt;&lt;/select&gt; has wrong number of children ["option"] in &lt;table&gt;&lt;tr&gt;&lt;td&gt;&lt;select&gt;&lt;option&gt;&lt;hr&gt;.
    Expected: 2
      Actual: 1

now we'll see:

    TestHtml5TreeConstructionWebkit02#test_31 [/home/flavorjones/code/oss/nokogiri/test/html5/test_tree_construction.rb:35]
    Minitest::Assertion: Element &lt;select&gt; has wrong number of children ["option"]
       Input: &lt;table&gt;&lt;tr&gt;&lt;td&gt;&lt;select&gt;&lt;option&gt;&lt;hr&gt;
    Expected: | &lt;html&gt;
              |   &lt;head&gt;
              |   &lt;body&gt;
              |     &lt;table&gt;
              |       &lt;tbody&gt;
              |         &lt;tr&gt;
              |           &lt;td&gt;
              |             &lt;select&gt;
              |               &lt;option&gt;
              |               &lt;hr&gt;
      Parsed: &lt;select&gt;&lt;option&gt;&lt;hr&gt;&lt;/option&gt;&lt;/select&gt;.
    Expected: 2
      Actual: 1
diff --git a/test/html5/test_tree_construction.rb b/test/html5/test_tree_construction.rb
@@ -35,7 +35,12 @@ def compare_nodes(node, ng_node)
       assert_equal(
         node[:children].length,
         ng_node.children.length,
-        "Element <#{node[:tag]}> has wrong number of children #{ng_node.children.map(&:name)} in #{@test[:data]}",
+        [
+          "Element <#{node[:tag]}> has wrong number of children #{ng_node.children.map(&:name)}",
+          "   Input: #{@test[:data]}",
+          "Expected: #{@test[:raw].join("\n          ")}",
+          "  Parsed: #{ng_node.to_html}",
+        ].join("\n"),
       )
     when Nokogiri::XML::Node::TEXT_NODE, Nokogiri::XML::Node::CDATA_SECTION_NODE
       # We preserve the CDATA in the tree, but the tests represent it as text.
@@ -205,8 +210,10 @@ def self.parse_test(test_data)
       children: [],
     }
     open_nodes = [document]
+    test[:raw] = []
     while index < lines.length
       raise(BadHtml5libFormat, "Expected '| ' but got #{lines[index]}") unless /^\| ( *)([^ ].*$)/ =~ lines[index]
+      test[:raw] << lines[index]
 
       depth = $LAST_MATCH_INFO[1].length
       if depth.odd?
