diff --git a/.github/workflows/php.yml b/.github/workflows/php.yml
index 0d2579d..2d47ab6 100644
--- a/.github/workflows/php.yml
+++ b/.github/workflows/php.yml
@@ -36,4 +36,4 @@ jobs:
     # Docs: https://getcomposer.org/doc/articles/scripts.md
 
     - name: Run test suite
-      run: vendor/bin/phpunit
+      run: composer run-script test
diff --git a/composer.json b/composer.json
index 305fb3c..c1ff20f 100644
--- a/composer.json
+++ b/composer.json
@@ -19,10 +19,19 @@
         "psr-0": { "ivuorinen\\Palette\\": "src/" },
         "classmap": ["src/"]
     },
+    "autoload-dev": {
+        "psr-0": {
+            "ivuorinen\\Palette\\Tests\\": "tests/"
+        }
+    },
     "require": {
         "php": ">=5.6.0"
     },
     "require-dev": {
-        "phpunit/phpunit": "9.5.21"
+        "phpunit/phpunit": "9.5.21",
+        "squizlabs/php_codesniffer": "^3.7"
+    },
+    "scripts": {
+        "test": "vendor/bin/phpunit"
     }
 }
diff --git a/phpcs.xml.dist b/phpcs.xml.dist
new file mode 100644
index 0000000..1decab6
--- /dev/null
+++ b/phpcs.xml.dist
@@ -0,0 +1,21 @@
+<?xml version="1.0"?>
+<ruleset
+        name="PHP_CodeSniffer"
+        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:noNamespaceSchemaLocation="https://raw.githubusercontent.com/squizlabs/PHP_CodeSniffer/master/phpcs.xsd"
+>
+    <description>PHP Code Sniffer configuration file.</description>
+
+    <file>.</file>
+
+    <arg name="basepath" value="."/>
+    <arg name="colors"/>
+    <arg name="extensions" value="php"/>
+    <arg name="parallel" value="10"/>
+
+    <!-- base rule: set to PSR12-->
+    <!-- https://www.php-fig.org/psr/psr-12/ -->
+    <rule ref="PSR12">
+        <exclude-pattern>*/vendor/*</exclude-pattern>
+    </rule>
+</ruleset>
diff --git a/tests/PaletteTest.php b/tests/PaletteTest.php
index abb0af0..833ff51 100644
--- a/tests/PaletteTest.php
+++ b/tests/PaletteTest.php
@@ -1,23 +1,27 @@
 <?php
 
-class PaletteTest extends \PHPUnit_Framework_TestCase
+namespace ivuorinen\Palette\Tests;
+
+use PHPUnit\Framework\TestCase;
+
+class PaletteTest extends TestCase
 {
-    public function test_class_is_found_and_has_default_attributes()
+    public function testClassIsFoundAndHasDefaultAttributes()
     {
         $palette = new \ivuorinen\Palette\Palette();
         $this->assertInstanceOf('ivuorinen\Palette\Palette', $palette);
 
-        $this->assertInternalType('integer', $palette->precision);
-        $this->assertInternalType('integer', $palette->returnColors);
-        $this->assertInternalType('array', $palette->colorsArray);
-        $this->assertInternalType('null', $palette->filename);
-        $this->assertInternalType('string', $palette->destination);
+        $this->assertIsInt($palette->precision);
+        $this->assertIsInt($palette->returnColors);
+        $this->assertIsArray($palette->colorsArray);
+        $this->assertNull($palette->filename);
+        $this->assertIsString($palette->destination);
     }
 
-    public function test_known_images_with_one_color()
+    public function testKnownImagesWithOneColor()
     {
         $location = __DIR__ . DIRECTORY_SEPARATOR . 'assets' . DIRECTORY_SEPARATOR;
-        $images = ['black.png' => '000000', 'red.png' => 'CC3333'];
+        $images   = [ 'black.png' => '000000', 'red.png' => 'CC3333' ];
 
         foreach ($images as $imageFile => $hex) {
             $image = $location . $imageFile;
@@ -30,10 +34,10 @@ class PaletteTest extends \PHPUnit_Framework_TestCase
         }
     }
 
-    public function test_known_images_with_many_colors()
+    public function testKnownImagesWithManyColors()
     {
         $location = __DIR__ . DIRECTORY_SEPARATOR . 'assets' . DIRECTORY_SEPARATOR;
-        $images = ['example.gif', 'example.jpg', 'example.png'];
+        $images   = [ 'example.gif', 'example.jpg', 'example.png' ];
 
         foreach ($images as $imageFile) {
             $image = $location . $imageFile;
@@ -45,20 +49,21 @@ class PaletteTest extends \PHPUnit_Framework_TestCase
         }
     }
 
-    public function test_failure_no_image()
+    public function testFailureNoImage()
     {
         $palette = new \ivuorinen\Palette\Palette('');
-        $this->expectException(ErrorException::class);
+        $this->expectException(\ErrorException::class);
         $this->expectExceptionMessage('Image was not provided');
         $palette->getPalette();
     }
 
-    public function test_failure_not_an_image()
+    public function testFailureNotAnImage()
     {
-        $palette = new \ivuorinen\Palette\Palette();
+        $palette           = new \ivuorinen\Palette\Palette();
         $palette->filename = 'NOT_HERE';
-        $this->expectException(ErrorException::class);
+        $this->expectException(\ErrorException::class);
         $this->expectExceptionMessage('Image ' . $palette->filename . ' is not readable');
+
         $palette->getPalette();
     }
 }