Improve Driver Specializing Process (#1315)

Streamline driver specializing process of analyzers, modifers, encoders and decoders.

tests/Unit/Drivers/SpecializableDecoderTest.php

@@ -0,0 +1,20 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Intervention\Image\Tests\Unit\Drivers;
+
+use Intervention\Image\Drivers\SpecializableDecoder;
+use Intervention\Image\Exceptions\DecoderException;
+use Intervention\Image\Tests\BaseTestCase;
+use Mockery;
+
+final class SpecializableDecoderTest extends BaseTestCase
+{
+    public function testDecode(): void
+    {
+        $decoder = Mockery::mock(SpecializableDecoder::class)->makePartial();
+        $this->expectException(DecoderException::class);
+        $decoder->decode(null);
+    }
+}