[TASK] Make RuleSet concrete

... adding internal `render` method.

Precursor to #1194.

Author: JakeQZ

src/RuleSet/RuleSet.php

@@ -27,7 +27,7 @@
  * Note that `CSSListItem` extends both `Commentable` and `Renderable`,
  * so those interfaces must also be implemented by concrete subclasses.
  */
-abstract class RuleSet implements CSSElement, CSSListItem, Positionable, RuleContainer
+class RuleSet implements CSSElement, CSSListItem, Positionable, RuleContainer
 {
     use CommentContainer;
     use Position;
@@ -293,6 +293,14 @@ public function removeAllRules(): void
         $this->rules = [];
     }
 
+    /**
+     * @internal
+     */
+    public function render(OutputFormat $outputFormat): string
+    {
+        return $this->renderRules($outputFormat);
+    }
+
     protected function renderRules(OutputFormat $outputFormat): string
     {
         $result = '';

tests/Unit/RuleSet/Fixtures/ConcreteRuleSet.php

@@ -7,7 +7,9 @@
 use PHPUnit\Framework\TestCase;
 use Sabberworm\CSS\CSSElement;
 use Sabberworm\CSS\CSSList\CSSListItem;
-use Sabberworm\CSS\Tests\Unit\RuleSet\Fixtures\ConcreteRuleSet;
+use Sabberworm\CSS\OutputFormat;
+use Sabberworm\CSS\Rule\Rule;
+use Sabberworm\CSS\RuleSet\RuleSet;
 
 /**
  * @covers \Sabberworm\CSS\RuleSet\RuleSet
@@ -17,13 +19,13 @@ final class RuleSetTest extends TestCase
     use RuleContainerTest;
 
     /**
-     * @var ConcreteRuleSet
+     * @var RuleSet
      */
     private $subject;
 
     protected function setUp(): void
     {
-        $this->subject = new ConcreteRuleSet();
+        $this->subject = new RuleSet();
     }
 
     /**
@@ -41,4 +43,59 @@ public function implementsCSSListItem(): void
     {
         self::assertInstanceOf(CSSListItem::class, $this->subject);
     }
+
+    /**
+     * @return array<string, array{0: list<array{name: string, value: string}>, 1: string}>
+     */
+    public static function providePropertyNamesAndValuesAndExpectedCss(): array
+    {
+        return [
+            'no properties' => [[], ''],
+            'one property' => [
+                [['name' => 'color', 'value' => 'green']],
+                'color: green;',
+            ],
+            'two different properties' => [
+                [
+                    ['name' => 'color', 'value' => 'green'],
+                    ['name' => 'display', 'value' => 'block'],
+                ],
+                'color: green;display: block;',
+            ],
+            'two of the same property' => [
+                [
+                    ['name' => 'color', 'value' => '#40A040'],
+                    ['name' => 'color', 'value' => 'rgba(0, 128, 0, 0.25)'],
+                ],
+                'color: #40A040;color: rgba(0, 128, 0, 0.25);',
+            ],
+        ];
+    }
+
+    /**
+     * @test
+     *
+     * @param list<array{name: string, value: string}> $propertyNamesAndValuesToSet
+     *
+     * @dataProvider providePropertyNamesAndValuesAndExpectedCss
+     */
+    public function renderReturnsCssForRulesSet(array $propertyNamesAndValuesToSet, string $expectedCss): void
+    {
+        $rulesToSet = \array_map(
+            /**
+             * @param array{name: string, value: string} $nameAndValue
+             */
+            static function (array $nameAndValue): Rule {
+                $rule = new Rule($nameAndValue['name']);
+                $rule->setValue($nameAndValue['value']);
+                return $rule;
+            },
+            $propertyNamesAndValuesToSet
+        );
+        $this->subject->setRules($rulesToSet);
+
+        $result = $this->subject->render(OutputFormat::create());
+
+        self::assertSame($expectedCss, $result);
+    }
 }