Make Image::setInstance method protected

Author: natanfelles

src/Image.php

@@ -123,7 +123,7 @@ public function getInstance() : GdImage
      *
      * @return static
      */
-    public function setInstance(GdImage $instance) : static
+    protected function setInstance(GdImage $instance) : static
     {
         $this->instance = $instance;
         return $this;

tests/ImageTest.php

@@ -83,13 +83,6 @@ public function testResolution() : void
     public function testInstance() : void
     {
         self::assertInstanceOf(\GdImage::class, $this->image->getInstance());
-        $instance = \imagecreatefrompng(__DIR__ . '/Support/tree.png');
-        self::assertNotSame($instance, $this->image->getInstance());
-        $this->image->setInstance($instance); // @phpstan-ignore-line
-        self::assertSame($instance, $this->image->getInstance());
-        $this->expectException(\TypeError::class);
-        $instance = \fopen(__FILE__, 'rb');
-        $this->image->setInstance($instance); // @phpstan-ignore-line
     }
 
     public function testQualityPng() : void