test(conformance): add #[CoversClass] and #[Test] to ImmutableStateTest; fix README stats (19→20 files)

Author: walmir-silva

README.md

@@ -228,8 +228,8 @@ src/
 
 | Metric | Value |
 |---|---|
-| PHP source files | 19 |
-| Source lines | ~720 |
+| PHP source files | 20 |
+| Source lines | ~810 |
 | Test files | 13 |
 | Test lines | ~700 |
 | External runtime dependencies | 1 (kariricode/property-inspector) |

tests/Conformance/ImmutableStateTest.php

@@ -5,10 +5,14 @@
 namespace KaririCode\Serializer\Tests\Conformance;
 
 use KaririCode\Serializer\Core\SerializationContextImpl;
+use PHPUnit\Framework\Attributes\CoversClass;
+use PHPUnit\Framework\Attributes\Test;
 use PHPUnit\Framework\TestCase;
 
+#[CoversClass(SerializationContextImpl::class)]
 final class ImmutableStateTest extends TestCase
 {
+    #[Test]
     public function testContextImmutability(): void
     {
         $ctx = SerializationContextImpl::create('json');
@@ -18,6 +22,7 @@ public function testContextImmutability(): void
         $this->assertSame('xml', $ctx2->getFormat());
     }
 
+    #[Test]
     public function testParametersImmutability(): void
     {
         $ctx = SerializationContextImpl::create();