[TASK] Add more unit tests for Document

Part of #757

Author: oliverklee

tests/Unit/CSSList/DocumentTest.php

@@ -12,6 +12,8 @@
 
 /**
  * @covers \Sabberworm\CSS\CSSList\Document
+ * @covers \Sabberworm\CSS\CSSList\CSSBlockList
+ * @covers \Sabberworm\CSS\CSSList\CSSList
  */
 final class DocumentTest extends TestCase
 {
@@ -31,6 +33,16 @@ public function implementsCommentable(): void
         self::assertInstanceOf(Commentable::class, new Document());
     }
 
+    /**
+     * @test
+     */
+    public function getAllDeclarationBlocksInitiallyReturnsEmptyArray(): void
+    {
+        $subject = new Document();
+
+        self::assertSame([], $subject->getAllDeclarationBlocks());
+    }
+
     /**
      * @test
      */
@@ -142,4 +154,14 @@ public function insertContentBeforeAppendsIfSiblingNotFound(): void
         self::assertCount(4, $subject->getContents());
         self::assertSame([$bogusOne, $sibling, $bogusTwo, $item], $subject->getContents());
     }
+
+    /**
+     * @test
+     */
+    public function isRootListAlwaysReturnsTrue(): void
+    {
+        $subject = new Document();
+
+        self::assertTrue($subject->isRootList());
+    }
 }