Add example indexing and rendering test

tests/data/example_numbering_001.xml

@@ -0,0 +1,31 @@
+<chapter xml:id="example-numbering">
+ <section>
+  <example>
+    <title>- 1. example without an xml:id</title>
+  </example>
+ </section>
+
+ <section>
+  <example>
+    <title>- 2. example without an xml:id</title>
+  </example>
+ </section>
+
+ <section>
+  <example xml:id="third-example-id">
+    <title>- 3. example with an xml:id</title>
+  </example>
+ </section>
+
+ <section>
+  <example>
+    <title>- 4. example without an xml:id</title>
+  </example>
+ </section>
+
+ <section>
+  <example>
+    <title>- 5. example without an xml:id</title>
+  </example>
+ </section>
+</chapter>

tests/example_numbering_001.phpt

@@ -0,0 +1,87 @@
+--TEST--
+Example numbering 001 - indexing and rendering examples with and without an xml:id
+--FILE--
+<?php
+namespace phpdotnet\phd;
+
+require_once __DIR__ . "/setup.php";
+
+$xml_file = __DIR__ . "/data/example_numbering_001.xml";
+
+Config::init([
+    "force_index"    => true,
+    "xml_file" => $xml_file,
+]);
+
+$indexRepository = new IndexRepository(new \SQLite3(":memory:"));
+$indexRepository->init();
+Config::set_indexcache($indexRepository);
+
+$index = new TestIndex($indexRepository);
+
+$render = new TestRender(new Reader, new Config, null, $index);
+
+$render->run();
+
+$indexes = array_keys($index->getNfo());
+
+echo "Indexes stored:\n";
+
+var_dump($indexes);
+
+$format = new TestGenericChunkedXHTML;
+
+$render = new TestRender(new Reader, new Config, $format);
+
+$render->run();
+
+?>
+--EXPECT--
+Indexes stored:
+array(6) {
+  [0]=>
+  string(17) "example-numbering"
+  [1]=>
+  string(9) "example-1"
+  [2]=>
+  string(9) "example-2"
+  [3]=>
+  string(16) "third-example-id"
+  [4]=>
+  string(9) "example-4"
+  [5]=>
+  string(9) "example-5"
+}
+Filename: example-numbering.html
+Content:
+<div id="example-numbering" class="chapter">
+ <div class="section">
+  <div class="example" id="example-1">
+    <p><strong>Example #1 - 1. example without an xml:id</strong></p>
+  </div>
+ </div>
+
+ <div class="section">
+  <div class="example" id="example-2">
+    <p><strong>Example #2 - 2. example without an xml:id</strong></p>
+  </div>
+ </div>
+
+ <div class="section">
+  <div class="example" id="third-example-id">
+    <p><strong>Example #3 - 3. example with an xml:id</strong></p>
+  </div>
+ </div>
+
+ <div class="section">
+  <div class="example" id="example-4">
+    <p><strong>Example #4 - 4. example without an xml:id</strong></p>
+  </div>
+ </div>
+
+ <div class="section">
+  <div class="example" id="example-5">
+    <p><strong>Example #5 - 5. example without an xml:id</strong></p>
+  </div>
+ </div>
+</div>