Add QuantizeColorsModifier tests

tests/Drivers/Gd/Modifiers/QuantizeColorsModifierTest.php

@@ -0,0 +1,42 @@
+<?php
+
+namespace Intervention\Image\Tests\Drivers\Gd\Modifiers;
+
+use Intervention\Image\Interfaces\ImageInterface;
+use Intervention\Image\Modifiers\QuantizeColorsModifier;
+use Intervention\Image\Tests\TestCase;
+use Intervention\Image\Tests\Traits\CanCreateGdTestImage;
+
+/**
+ * @requires extension gd
+ * @covers \Intervention\Image\Modifiers\QuantizeColorsModifier
+ */
+class QuantizeColorsModifierTest extends TestCase
+{
+    use CanCreateGdTestImage;
+
+    public function testColorChange(): void
+    {
+        $image = $this->readTestImage('gradient.bmp');
+        $this->assertColorCount(15, $image);
+        $image->modify(new QuantizeColorsModifier(4));
+        $this->assertColorCount(4, $image);
+    }
+
+    private function assertColorCount(int $count, ImageInterface $image): void
+    {
+        $colors = [];
+        $width = $image->width();
+        $height = $image->height();
+        for ($x = 0; $x < $width; $x++) {
+            for ($y = 0; $y < $height; $y++) {
+                $rgb = imagecolorat($image->core()->native(), $x, $y);
+                $color = imagecolorsforindex($image->core()->native(), $rgb);
+                $color = implode('-', $color);
+                $colors[$color] = $color;
+            }
+        }
+
+        $this->assertEquals(count($colors), $count);
+    }
+}

tests/Drivers/Imagick/Modifiers/QuantizeColorsModifierTest.php

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+<?php
+
+namespace Intervention\Image\Tests\Drivers\Imagick\Modifiers;
+
+use Intervention\Image\Modifiers\QuantizeColorsModifier;
+use Intervention\Image\Tests\TestCase;
+use Intervention\Image\Tests\Traits\CanCreateImagickTestImage;
+
+/**
+ * @requires extension imagick
+ * @covers \Intervention\Image\Modifiers\QuantizeColorsModifier
+ */
+class QuantizeColorsModifierTest extends TestCase
+{
+    use CanCreateImagickTestImage;
+
+    public function testColorChange(): void
+    {
+        $image = $this->readTestImage('gradient.bmp');
+        $this->assertEquals(15, $image->core()->native()->getImageColors());
+        $image->modify(new QuantizeColorsModifier(4));
+        $this->assertEquals(4, $image->core()->native()->getImageColors());
+    }
+}