diff --git a/tests/Colors/Cmyk/Decoders/StringColorDecoderTest.php b/tests/Colors/Cmyk/Decoders/StringColorDecoderTest.php
index f73093c8..2dd30ed8 100644
--- a/tests/Colors/Cmyk/Decoders/StringColorDecoderTest.php
+++ b/tests/Colors/Cmyk/Decoders/StringColorDecoderTest.php
@@ -6,6 +6,7 @@ namespace Intervention\Image\Tests\Colors\Cmyk\Decoders;
 
 use Intervention\Image\Colors\Cmyk\Color;
 use Intervention\Image\Colors\Cmyk\Decoders\StringColorDecoder;
+use Intervention\Image\Exceptions\DecoderException;
 use Intervention\Image\Tests\TestCase;
 
 /**
@@ -29,9 +30,15 @@ class StringColorDecoderTest extends TestCase
         $this->assertInstanceOf(Color::class, $result);
         $this->assertEquals([0, 100, 100, 0], $result->toArray());
 
-
         $result = $decoder->decode('cmyk(0%, 100%, 100%, 0%)');
         $this->assertInstanceOf(Color::class, $result);
         $this->assertEquals([0, 100, 100, 0], $result->toArray());
     }
+
+    public function testDecodeInvalid(): void
+    {
+        $decoder = new StringColorDecoder();
+        $this->expectException(DecoderException::class);
+        $decoder->decode(null);
+    }
 }
diff --git a/tests/Drivers/Gd/Modifiers/QuantizeColorsModifierTest.php b/tests/Drivers/Gd/Modifiers/QuantizeColorsModifierTest.php
index 8d0435ec..8343b40d 100644
--- a/tests/Drivers/Gd/Modifiers/QuantizeColorsModifierTest.php
+++ b/tests/Drivers/Gd/Modifiers/QuantizeColorsModifierTest.php
@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Intervention\Image\Tests\Drivers\Gd\Modifiers;
 
+use Intervention\Image\Exceptions\InputException;
 use Intervention\Image\Interfaces\ImageInterface;
 use Intervention\Image\Modifiers\QuantizeColorsModifier;
 use Intervention\Image\Tests\TestCase;
@@ -26,6 +27,21 @@ class QuantizeColorsModifierTest extends TestCase
         $this->assertColorCount(4, $image);
     }
 
+    public function testNoColorReduction(): void
+    {
+        $image = $this->readTestImage('gradient.bmp');
+        $this->assertColorCount(15, $image);
+        $image->modify(new QuantizeColorsModifier(150));
+        $this->assertColorCount(15, $image);
+    }
+
+    public function testInvalidColorInput(): void
+    {
+        $image = $this->readTestImage('gradient.bmp');
+        $this->expectException(InputException::class);
+        $image->modify(new QuantizeColorsModifier(0));
+    }
+
     private function assertColorCount(int $count, ImageInterface $image): void
     {
         $colors = [];
diff --git a/tests/Drivers/Gd/Modifiers/RemoveAnimationModifierTest.php b/tests/Drivers/Gd/Modifiers/RemoveAnimationModifierTest.php
index f46950da..ea190c6a 100644
--- a/tests/Drivers/Gd/Modifiers/RemoveAnimationModifierTest.php
+++ b/tests/Drivers/Gd/Modifiers/RemoveAnimationModifierTest.php
@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Intervention\Image\Tests\Drivers\Gd\Modifiers;
 
+use Intervention\Image\Exceptions\InputException;
 use Intervention\Image\Modifiers\RemoveAnimationModifier;
 use Intervention\Image\Tests\TestCase;
 use Intervention\Image\Tests\Traits\CanCreateGdTestImage;
@@ -34,4 +35,11 @@ class RemoveAnimationModifierTest extends TestCase
         $this->assertEquals(1, count($image));
         $this->assertEquals(1, count($result));
     }
+
+    public function testApplyInvalid(): void
+    {
+        $image = $this->readTestImage('animation.gif');
+        $this->expectException(InputException::class);
+        $image->modify(new RemoveAnimationModifier('test'));
+    }
 }
diff --git a/tests/Drivers/Imagick/Modifiers/QuantizeColorsModifierTest.php b/tests/Drivers/Imagick/Modifiers/QuantizeColorsModifierTest.php
index cf0e860b..29bc62ef 100644
--- a/tests/Drivers/Imagick/Modifiers/QuantizeColorsModifierTest.php
+++ b/tests/Drivers/Imagick/Modifiers/QuantizeColorsModifierTest.php
@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Intervention\Image\Tests\Drivers\Imagick\Modifiers;
 
+use Intervention\Image\Exceptions\InputException;
 use Intervention\Image\Modifiers\QuantizeColorsModifier;
 use Intervention\Image\Tests\TestCase;
 use Intervention\Image\Tests\Traits\CanCreateImagickTestImage;
@@ -24,4 +25,19 @@ class QuantizeColorsModifierTest extends TestCase
         $image->modify(new QuantizeColorsModifier(4));
         $this->assertEquals(4, $image->core()->native()->getImageColors());
     }
+
+    public function testNoColorReduction(): void
+    {
+        $image = $this->readTestImage('gradient.bmp');
+        $this->assertEquals(15, $image->core()->native()->getImageColors());
+        $image->modify(new QuantizeColorsModifier(150));
+        $this->assertEquals(15, $image->core()->native()->getImageColors());
+    }
+
+    public function testInvalidColorInput(): void
+    {
+        $image = $this->readTestImage('gradient.bmp');
+        $this->expectException(InputException::class);
+        $image->modify(new QuantizeColorsModifier(0));
+    }
 }
diff --git a/tests/Drivers/Imagick/Modifiers/RemoveAnimationModifierTest.php b/tests/Drivers/Imagick/Modifiers/RemoveAnimationModifierTest.php
index 9ca4c126..c12fb96e 100644
--- a/tests/Drivers/Imagick/Modifiers/RemoveAnimationModifierTest.php
+++ b/tests/Drivers/Imagick/Modifiers/RemoveAnimationModifierTest.php
@@ -4,6 +4,7 @@ declare(strict_types=1);
 
 namespace Intervention\Image\Tests\Drivers\Imagick\Modifiers;
 
+use Intervention\Image\Exceptions\InputException;
 use Intervention\Image\Modifiers\RemoveAnimationModifier;
 use Intervention\Image\Tests\TestCase;
 use Intervention\Image\Tests\Traits\CanCreateImagickTestImage;
@@ -34,4 +35,11 @@ class RemoveAnimationModifierTest extends TestCase
         $this->assertEquals(1, count($image));
         $this->assertEquals(1, count($result));
     }
+
+    public function testApplyInvalid(): void
+    {
+        $image = $this->readTestImage('animation.gif');
+        $this->expectException(InputException::class);
+        $image->modify(new RemoveAnimationModifier('test'));
+    }
 }