diff --git a/phpunit.xml b/phpunit.xml
index 309c0de..771a9be 100644
--- a/phpunit.xml
+++ b/phpunit.xml
@@ -12,6 +12,9 @@
         <testsuite name="default">
             <directory>tests</directory>
         </testsuite>
+        <testsuite name="helper">
+            <directory>tests/Helper</directory>
+        </testsuite>
     </testsuites>
 
     <source restrictDeprecations="true" restrictNotices="true" restrictWarnings="true">
diff --git a/src/CountingSort.php b/src/CountingSort.php
new file mode 100644
index 0000000..b7cad49
--- /dev/null
+++ b/src/CountingSort.php
@@ -0,0 +1,37 @@
+<?php
+
+namespace Src;
+
+use Src\helper\ArrayHelper;
+
+class CountingSort
+{
+    /**
+     * @param array<int> $arr
+     * @return array<int>
+     */
+    public static function sort(array $arr): array
+    {
+        $length = count($arr);
+        if ($length <= 1) {
+            return $arr;
+        }
+        $minElement = ArrayHelper::getMin($arr);
+        $maxElement = ArrayHelper::getMax($arr);
+        $helperArray = [];
+        for ($i = $minElement; $i <= $maxElement; $i++) {
+            $helperArray[$i] = 0;
+        }
+        foreach ($arr as $element) {
+            $helperArray[$element]++;
+        }
+        for ($i = $minElement + 1; $i <= $maxElement; $i++) {
+            $helperArray[$i] += $helperArray[$i - 1];
+        }
+        $resultArray = [];
+        for ($i = 0; $i < $length; $i++) {
+            $resultArray[--$helperArray[$arr[$i]]] = $arr[$i];
+        }
+        return $resultArray;
+    }
+}
diff --git a/src/helper/ArrayHelper.php b/src/helper/ArrayHelper.php
new file mode 100644
index 0000000..1d11e89
--- /dev/null
+++ b/src/helper/ArrayHelper.php
@@ -0,0 +1,56 @@
+<?php
+
+namespace Src\helper;
+
+class ArrayHelper
+{
+    /**
+     * Returns the smallest value of the array
+     *
+     * @param array<int, int|float> $array
+     * @return int|float
+     */
+    public static function getMin(array $array): int|float
+    {
+        return min($array);
+    }
+
+    /**
+     * Returns the biggest value of the array
+     *
+     * @param array<int, int|float> $array
+     * @return int|float
+     */
+    public static function getMax(array $array): int|float
+    {
+        return max($array);
+    }
+
+    /**
+     * Checks the array for non int values and return false if any occur
+     *
+     * @param array<int, mixed> $array
+     * @return bool
+     */
+    public static function consistsOfInt(array $array): bool
+    {
+        return count($array) == count(array_filter($array, 'is_int'));
+    }
+
+    /**
+     * Checks the array is sorted
+     *
+     * @param array<int, mixed> $array
+     * @return bool
+     */
+    public static function isSorted(array $array): bool
+    {
+        $length = count($array);
+        for ($i = 0; $i < $length - 1; $i++) {
+            if ($array[$i] > $array[$i + 1]) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
diff --git a/tests/CountingSortTest.php b/tests/CountingSortTest.php
new file mode 100644
index 0000000..d4c4f10
--- /dev/null
+++ b/tests/CountingSortTest.php
@@ -0,0 +1,57 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests;
+
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Src\CountingSort;
+
+final class CountingSortTest extends TestCase
+{
+    #[Test]
+    #[DataProvider('arrayProvider')]
+    /**
+     * @param array<int> $arr
+     */
+    public function it_should_return_the_sorted_array(array $arr): void
+    {
+        $this->assertEquals([1, 2, 3, 4, 5, 6, 7, 8, 9], CountingSort::sort($arr));
+    }
+
+    /**
+     * @return array<array<int>>
+     */
+    public static function arrayProvider(): array
+    {
+        return [
+            [[1, 2, 3, 4, 5, 6, 7, 8, 9]],
+            [[9, 8, 7, 6, 5, 4, 3, 2, 1]],
+            [[1, 2, 3, 9, 8, 7, 6, 5, 4]],
+            [[9, 8, 7, 1, 2, 3, 4, 5, 6]],
+            [[9, 1, 8, 2, 7, 3, 6, 4, 5]],
+            [[1, 9, 2, 8, 3, 7, 4, 6, 5]],
+            [[6, 4, 1, 8, 3, 9, 2, 5, 7]],
+        ];
+    }
+
+    #[Test]
+    public function it_should_sort_single_element_array(): void
+    {
+        $this->assertEquals([4], CountingSort::sort([4]));
+    }
+
+    #[Test]
+    public function test_empty_array(): void
+    {
+        $this->assertEquals([], CountingSort::sort([]));
+    }
+
+    #[Test]
+    public function it_should_sort_non_consecutive_numbers_correctly(): void
+    {
+        $this->assertEquals([2, 5, 6, 8, 9], CountingSort::sort([5, 9, 6, 2, 8]));
+    }
+}
diff --git a/tests/Helper/ArrayHelperTest.php b/tests/Helper/ArrayHelperTest.php
new file mode 100644
index 0000000..c6f936f
--- /dev/null
+++ b/tests/Helper/ArrayHelperTest.php
@@ -0,0 +1,91 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Tests\Helper;
+
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\Attributes\Test;
+use PHPUnit\Framework\TestCase;
+use Src\helper\ArrayHelper;
+
+final class ArrayHelperTest extends TestCase
+{
+    #[Test]
+    #[DataProvider('minMaxProvider')]
+    public function it_should_return_the_minimum_value(array $array, int|float $expectedMin): void
+    {
+        $this->assertEquals($expectedMin, ArrayHelper::getMin($array));
+    }
+
+    #[Test]
+    #[DataProvider('minMaxProvider')]
+    public function it_should_return_the_maximum_value(array $array, int|float $expectedMin, int|float $expectedMax): void
+    {
+        $this->assertEquals($expectedMax, ArrayHelper::getMax($array));
+    }
+
+    #[Test]
+    #[DataProvider('intValidationProvider')]
+    public function it_should_check_if_array_consists_of_only_integers(array $array, bool $expected): void
+    {
+        $this->assertEquals($expected, ArrayHelper::consistsOfInt($array));
+    }
+
+    #[Test]
+    #[DataProvider('isSortedProvider')]
+    public function it_should_check_if_array_is_sorted(array $array, bool $expected): void
+    {
+        $this->assertEquals($expected, ArrayHelper::isSorted($array));
+    }
+
+    /**
+     * Provides data for min and max tests
+     *
+     * @return array<int, array<int, mixed>>
+     */
+    public static function minMaxProvider(): array
+    {
+        return [
+            [[1, 2, 3, 4, 5], 1, 5],
+            [[-10, 0, 10, 20], -10, 20],
+            [[5.5, 2.2, 3.3, 4.4], 2.2, 5.5],
+            [[100], 100, 100],
+            [[-5, -10, -15], -15, -5],
+        ];
+    }
+
+    /**
+     * Provides data for integer validation test
+     *
+     * @return array<int, array<int, mixed>>
+     */
+    public static function intValidationProvider(): array
+    {
+        return [
+            [[1, 2, 3, 4, 5], true],
+            [[1.1, 2.2, 3.3], false],
+            [[1, 2, '3', 4], false],
+            [[], true],
+            [[100, -200, 0], true],
+        ];
+    }
+
+    /**
+     * Provides data for isSorted tests
+     *
+     * @return array<int, array<int, mixed>>
+     */
+    public static function isSortedProvider(): array
+    {
+        return [
+            [[1, 2, 3, 4, 5], true],   // Sorted ascending
+            [[5, 4, 3, 2, 1], false], // Descending
+            [[1, 1, 1, 1], true],     // All equal
+            [[], true],               // Empty array
+            [[10], true],             // Single element
+            [[1, 2, 2, 3, 4], true],  // Contains duplicates, sorted
+            [[1, 3, 2, 4], false],    // Unsorted
+        ];
+    }
+}