Test Parsedown against cached expect-to-pass CommonMark spec examples

This test suite runs tests the same way as `test/CommonMarkTestWeak.php`, but uses a cached set of CommonMark spec examples in `test/commonmark/`. It is executed along with Parsedown's default test suite and runs various CommonMark spec examples, which are expected to pass. If they don't pass, the Parsedown build fails. The intention of this test suite is to make sure, that previously passed CommonMark spec examples don't fail due to unwanted side-effects of code changes.

You can re-create the `test/commonmark/` directory by executing the PHPUnit group `update`. The test suite will then run `test/CommonMarkTestWeak.php` and create files with the Markdown source and the resulting HTML markup of all passed tests. The command to execute looks like the following:

    $ phpunit --group update

phpunit.xml.dist

@@ -3,6 +3,12 @@
 	<testsuites>
 		<testsuite name="ParsedownTests">
 			<file>tests/ParsedownTest.php</file>
+			<file>tests/CommonMarkTest.php</file>			
 		</testsuite>
 	</testsuites>
+	<groups>
+		<exclude>
+			<group>update</group>
+		</exclude>
+	</groups>
 </phpunit>

tests/CommonMarkTest.php

@@ -0,0 +1,110 @@
+<?php
+
+namespace Erusev\Parsedown\Tests;
+
+/**
+ * Test Parsedown against cached expect-to-pass CommonMark spec examples
+ *
+ * This test suite runs tests the same way as `test/CommonMarkTestWeak.php`,
+ * but uses a cached set of CommonMark spec examples in `test/commonmark/`.
+ * It is executed along with Parsedown's default test suite and runs various
+ * CommonMark spec examples, which are expected to pass. If they don't pass,
+ * the Parsedown build fails. The intention of this test suite is to make sure,
+ * that previously passed CommonMark spec examples don't fail due to unwanted
+ * side-effects of code changes.
+ *
+ * You can re-create the `test/commonmark/` directory by executing the PHPUnit
+ * group `update`. The test suite will then run `test/CommonMarkTestWeak.php`
+ * and create files with the Markdown source and the resulting HTML markup of
+ * all passed tests. The command to execute looks like the following:
+ *
+ *     $ phpunit --group update
+ *
+ * @link http://commonmark.org/ CommonMark
+ */
+class CommonMarkTest extends CommonMarkTestWeak
+{
+    /**
+     * @return array
+     */
+    public function data()
+    {
+        $data = [];
+
+        $dir = static::getDataDir();
+        $files = @\scandir($dir);
+        if (!empty($files)) {
+            foreach ($files as $file) {
+                if (($file === '.') || ($file === '..')) {
+                    continue;
+                }
+
+                if (\substr($file, -3) === '.md') {
+                    $testName = \substr($file, 0, -3);
+                    if (\file_exists($dir . $testName . '.html')) {
+                        \preg_match('/^(\d+)-(.*)$/', $testName, $matches);
+                        $id = isset($matches[1]) ? \intval($matches[1]) : 0;
+                        $section = isset($matches[2]) ? \preg_replace('/_+/', ' ', $matches[2]) : '';
+
+                        $markdown = \file_get_contents($dir . $testName . '.md');
+                        $expectedHtml = \file_get_contents($dir . $testName . '.html');
+
+                        $data[] = [
+                            'id' => $id,
+                            'section' => $section,
+                            'markdown' => $markdown,
+                            'expectedHtml' => $expectedHtml
+                        ];
+                    }
+                }
+            }
+        } else {
+            $this->fail('The CommonMark cache folder ' . $dir . ' is empty or not readable.');
+        }
+
+        return $data;
+    }
+
+    /**
+     * @group update
+     * @dataProvider dataUpdate
+     * @param $id
+     * @param $section
+     * @param $markdown
+     * @param $expectedHtml
+     */
+    public function testUpdateDatabase($id, $section, $markdown, $expectedHtml)
+    {
+        parent::testExample($id, $section, $markdown, $expectedHtml);
+
+        // you can only get here when the test passes
+        $dir = static::getDataDir(true);
+        $basename = $id . '-' . \preg_replace('/[^\w-.]/', '_', $section);
+        \file_put_contents($dir . $basename . '.md', $markdown);
+        \file_put_contents($dir . $basename . '.html', $expectedHtml);
+    }
+
+    /**
+     * @return array
+     */
+    public function dataUpdate()
+    {
+        return parent::data();
+    }
+
+    public static function getDataDir($mkdir = false)
+    {
+        $dir = __DIR__ . '/commonmark/';
+
+        if ($mkdir) {
+            if (!\file_exists($dir)) {
+                @\mkdir($dir);
+            }
+            if (!\is_dir($dir)) {
+                static::fail('Unable to create CommonMark cache folder ' . $dir . '.');
+            }
+        }
+
+        return $dir;
+    }
+}