add HTML driver

Author: Gummibeer

composer.json

@@ -21,6 +21,7 @@
     ],
     "require": {
         "php": "^7.2",
+        "ext-dom": "*",
         "phpunit/phpunit": "^8.0",
         "symfony/yaml": "^4.0"
     },

src/Drivers/HtmlDriver.php

@@ -0,0 +1,36 @@
+<?php
+
+namespace Spatie\Snapshots\Drivers;
+
+use DOMDocument;
+use PHPUnit\Framework\Assert;
+use Spatie\Snapshots\Driver;
+use Spatie\Snapshots\Exceptions\CantBeSerialized;
+
+class HtmlDriver implements Driver
+{
+    public function serialize($data): string
+    {
+        if (! is_string($data)) {
+            throw new CantBeSerialized('Only strings can be serialized to html');
+        }
+
+        $domDocument = new DOMDocument('1.0');
+        $domDocument->preserveWhiteSpace = false;
+        $domDocument->formatOutput = true;
+
+        @$domDocument->loadHTML($data); // to ignore HTML5 errors
+
+        return $domDocument->saveHTML();
+    }
+
+    public function extension(): string
+    {
+        return 'html';
+    }
+
+    public function match($expected, $actual)
+    {
+        Assert::assertEquals($expected, $this->serialize($actual));
+    }
+}

src/MatchesSnapshots.php

@@ -5,6 +5,7 @@
 use PHPUnit\Framework\ExpectationFailedException;
 use ReflectionClass;
 use ReflectionObject;
+use Spatie\Snapshots\Drivers\HtmlDriver;
 use Spatie\Snapshots\Drivers\JsonDriver;
 use Spatie\Snapshots\Drivers\VarDriver;
 use Spatie\Snapshots\Drivers\XmlDriver;
@@ -55,6 +56,11 @@ public function assertMatchesSnapshot($actual, Driver $driver = null)
         $this->doSnapshotAssertion($actual, $driver ?? new VarDriver());
     }
 
+    public function assertMatchesHtmlSnapshot($actual)
+    {
+        $this->assertMatchesSnapshot($actual, new HtmlDriver());
+    }
+
     public function assertMatchesXmlSnapshot($actual)
     {
         $this->assertMatchesSnapshot($actual, new XmlDriver());