[TASK] Extend and streamline KeyFrameTest

- use a per-test subject similar to #963
- add a missing `@covers` annotation for the parent class
- add tests for the line number

Part of #757

Author: oliverklee

tests/Unit/CSSList/KeyFrameTest.php

@@ -11,41 +11,60 @@
 use Sabberworm\CSS\Renderable;
 
 /**
+ * @covers \Sabberworm\CSS\CSSList\CSSList
  * @covers \Sabberworm\CSS\CSSList\KeyFrame
  */
 final class KeyFrameTest extends TestCase
 {
     /**
-     * @var KeyFrame
+     * @test
      */
-    private $subject;
+    public function implementsAtRule(): void
+    {
+        $subject = new KeyFrame();
+
+        self::assertInstanceOf(AtRule::class, $subject);
+    }
 
-    protected function setUp(): void
+    /**
+     * @test
+     */
+    public function implementsRenderable(): void
     {
-        $this->subject = new KeyFrame();
+        $subject = new KeyFrame();
+
+        self::assertInstanceOf(Renderable::class, $subject);
     }
 
     /**
      * @test
      */
-    public function implementsAtRule(): void
+    public function implementsCommentable(): void
     {
-        self::assertInstanceOf(AtRule::class, $this->subject);
+        $subject = new KeyFrame();
+
+        self::assertInstanceOf(Commentable::class, $subject);
     }
 
     /**
      * @test
      */
-    public function implementsRenderable(): void
+    public function getLineNoByDefaultReturnsZero(): void
     {
-        self::assertInstanceOf(Renderable::class, $this->subject);
+        $subject = new KeyFrame();
+
+        self::assertSame(0, $subject->getLineNo());
     }
 
     /**
      * @test
      */
-    public function implementsCommentable(): void
+    public function getLineNoReturnsLineNumberProvidedToConstructor(): void
     {
-        self::assertInstanceOf(Commentable::class, $this->subject);
+        $lineNumber = 42;
+
+        $subject = new KeyFrame($lineNumber);
+
+        self::assertSame($lineNumber, $subject->getLineNo());
     }
 }