diff --git a/Stdlib/Base/Heap.php b/Stdlib/Base/Heap.php
index e69de29bb..83af3ae15 100644
--- a/Stdlib/Base/Heap.php
+++ b/Stdlib/Base/Heap.php
@@ -0,0 +1,227 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 7.4
+ *
+ * @package    phpOMS\Stdlib\Base
+ * @copyright  Dennis Eichhorn
+ * @license    OMS License 1.0
+ * @version    1.0.0
+ * @link       https://orange-management.org
+ */
+declare(strict_types=1);
+
+namespace phpOMS\Stdlib\Base;
+
+/**
+ * Heap class.
+ *
+ * @package    phpOMS\Stdlib\Base
+ * @license    OMS License 1.0
+ * @link       https://orange-management.org
+ * @since      1.0.0
+ */
+class Heap
+{
+    private \Closure $compare = null;
+
+    private array $nodes = [];
+
+    public function __construct(\Closure $compare = null)
+    {
+        $this->compare = $compare ?? function($a, $b) { return $a <=> $b; };
+    }
+
+    public function insort($x, $lo = 0) : void
+    {
+        $hi = \count($this->nodes);
+
+        while ($lo < $hi) {
+            $mid = (int) \floor(($lo + $hi) / 2);
+            if ($this->compare($x, $this->node[$mid]) < 0) {
+                $hi = $mid;
+            } else {
+                $lo = $mid + 1;
+            }
+        }
+
+        $this->nodes = \array_splice($this->nodes, $lo, 0, $x);
+    }
+
+    public function push($item) : void
+    {
+        $this->nodes[] = $item;
+        $this->siftDown(0, \count($this->nodes) - 1);
+    }
+
+    public function pop()
+    {
+        $last = \array_pop($this->nodes);
+        if (empty($this->nodes)) {
+            return $last;
+        }
+
+        $item = $this->nodes[0];
+        $this->nodes[0] = $last;
+        $this->siftUp(0);
+
+        return $item;
+    }
+
+    public function peek()
+    {
+        return $this->nodes[0];
+    }
+
+    public function contains($item) : bool
+    {
+        foreach ($this->nodes as $key => $node) {
+            if (\is_scalar($item)) {
+                if ($node === $item) {
+                    return true;
+                }
+            } else {
+                if ($item->isEqual($node)) {
+                    return true;
+                }
+            }
+        }
+
+        return false;
+    }
+
+    public function replace($new)
+    {
+        $old = $this->nodes[0];
+        $this->nodes[0] = $new;
+        $this->siftUp(0);
+
+        return $old;
+    }
+
+    public function pushpop($item)
+    {
+        if (!empty($this->nodes) && $this->compare($this->nodes[0], $item) < 0) {
+            $temp = $item;
+            $item = $this->nodes[0];
+            $this->nodes[0] = $temp;
+            $this->siftUp(0);
+        }
+
+        return $item;
+    }
+
+    public function heapify() : void
+    {
+        for ($i = (int) \floor(\count($this->nodes) / 2); $i > -1; --$i) {
+            $this->siftUp($i);
+        }
+    }
+
+    public function update($item) : bool
+    {
+        $pos = null;
+        foreach ($this->nodes as $key => $node) {
+            if (\is_scalar($item)) {
+                if ($node === $item) {
+                    $pos = $key;
+                    break;
+                }
+            } else {
+                if ($item->isEqual($node)) {
+                    $pos = $key;
+                    break;
+                }
+            }
+        }
+
+        if ($pos === null) {
+            return false;
+        }
+
+        $this->siftDown(0, $pos);
+        $this->siftUp($pos);
+
+        return true;
+    }
+
+    public function getNLargest(int $n) : array
+    {
+        $nodes = $this->nodes;
+        \uasort($nodes, [$this, 'compare']);
+
+        return \array_slice($nodes, 0, $n);
+    }
+
+    public function getNSmallest(int $n): array
+    {
+        $nodes = $this->nodes;
+        \uasort($nodes, [$this, 'compare']);
+
+        return \array_slice(\array_reverse($nodes), 0, $n);
+    }
+
+    private function siftDown(int $start, int $pos) : void;
+    {
+        $item = $this->nodes[$pos];
+        while ($pos > $start) {
+            $pPos = ($pos - 1) >> 1;
+            $parent = $this->nodes[$pPos];
+
+            if ($this->compare($item, $parent) < 0) {
+                $this->nodes[$pos] = $parent;
+                $pos = $pPos;
+
+                continue;
+            }
+
+            break;
+        }
+
+        $this->nodes[$pos] = $item;
+    }
+
+    private function siftUp(int $pos) : void
+    {
+        $ePos = \count($this->nodes);
+        $sPos = $pos;
+        $item = $this->nodes[$pos];
+        $cPos = 2 * $pos + 1;
+
+        while ($cPos < $ePos) {
+            $rPos = $cPos + 1;
+
+            if ($rPos < $ePos && $this->compare($this->nodes[$cPos], $this->nodes[$rPos]) > -1) {
+                $cPos = $rPos;
+            }
+
+            $this->nodes[$pos] = $this->nodes[$cPos];
+            $pos = $cPos;
+            $cPos = 2 * $pos + 1;
+        }
+
+        $this->nodes[$pos] = $item;
+        $this->siftDown($sPos, $pos);
+    }
+
+    public function clear() : void
+    {
+        $this->nodes = [];
+    }
+
+    public function empty() : bool
+    {
+        return empty($this->nodes);
+    }
+
+    public function size() : int
+    {
+        return \count($this->nodes);
+    }
+
+    public function toArray()
+    {
+        return $this->nodes;
+    }
+}
diff --git a/tests/DataStorage/Database/TestModel/BaseModelMapper.php b/tests/DataStorage/Database/TestModel/BaseModelMapper.php
index 0baf99103..43398a3ea 100644
--- a/tests/DataStorage/Database/TestModel/BaseModelMapper.php
+++ b/tests/DataStorage/Database/TestModel/BaseModelMapper.php
@@ -57,7 +57,9 @@ class BaseModelMapper extends DataMapperAbstract
             'mapper'         => OwnsOneModelMapper::class,
             'dest'            => 'test_base_owns_one_self',
         ],
-    ];    /**
+    ];
+
+    /**
      * Has many relation.
      *
      * @var array<string, array<string, null|string>>
diff --git a/tests/Stdlib/Base/HeapTest.php b/tests/Stdlib/Base/HeapTest.php
new file mode 100644
index 000000000..8862a6036
--- /dev/null
+++ b/tests/Stdlib/Base/HeapTest.php
@@ -0,0 +1,167 @@
+<?php
+/**
+ * Orange Management
+ *
+ * PHP Version 7.4
+ *
+ * @package    tests
+ * @copyright  Dennis Eichhorn
+ * @license    OMS License 1.0
+ * @version    1.0.0
+ * @link       https://orange-management.org
+ */
+ declare(strict_types=1);
+
+namespace phpOMS\tests\Stdlib\Base;
+
+use phpOMS\Stdlib\Base\Heap;
+
+/**
+ * @internal
+ */
+class HeapTest extends \PHPUnit\Framework\TestCase
+{
+    public function testPushAndPop() : void
+    {
+        $heap = new Heap();
+        for ($i = 0; $i < 10; ++$i) {
+            $heap->push(\mt_rand());
+        }
+
+        $sorted = [];
+        while (!$heap->empty()) {
+            $sorted[] = $heap->pop();
+        }
+
+        $sortedFunction = $sorted;
+        \sort($sortedFunction);
+
+        self::assertEquals($sortedFunction, $sorted);
+    }
+
+    public function testPushAndPopCustomComparator() : void
+    {
+        $heap = new Heap(function($a, $b) { return ($a <=> $b) * -1; });
+        for ($i = 0; $i < 10; ++$i) {
+            $heap->push(\mt_rand());
+        }
+
+        $sorted = [];
+        while (!$heap->empty()) {
+            $sorted[] = $heap->pop();
+        }
+
+        $sortedFunction = $sorted;
+        \sort($sortedFunction);
+
+        self::assertEquals(\array_reverse($sortedFunction), $sorted);
+    }
+
+    public function testReplace() : void
+    {
+        $heap = new Heap();
+        for ($i = 1; $i < 6; ++$i) {
+            $heap->push($i);
+        }
+
+        self::assertEquals(1, $heap->replace(3));
+        self::assertEquals([2, 3, 3, 4, 5], $heap->toArray());
+    }
+
+    public function testPushPop() : void
+    {
+        $heap = new Heap();
+        for ($i = 1; $i < 6; ++$i) {
+            $heap->push($i);
+        }
+
+        self::assertEquals(1, $heap->pushpop(6));
+        self::assertEquals([2, 3, 4, 5, 6], $heap->toArray());
+    }
+
+    public function testContains(): void
+    {
+        $heap = new Heap();
+        for ($i = 1; $i < 6; ++$i) {
+            $heap->push($i);
+        }
+
+        self::assertTrue($heap->contains(1));
+        self::assertTrue($heap->contains(2));
+        self::assertTrue($heap->contains(3));
+        self::assertTrue($heap->contains(4));
+        self::assertTrue($heap->contains(5));
+        self::assertFalse($heap->contains(0));
+        self::assertFalse($heap->contains(6));
+    }
+
+    public function testPeek() : void
+    {
+        $heap = new Heap();
+
+        $heap->push(1);
+        self::assertEqals(1, $heap->peek());
+
+        $heap->push(2);
+        self::assertEqals(1, $heap->peek());
+
+        $heap->pop();
+        self::assertEqals(2, $heap->peek());
+    }
+
+    public function testNSmallest() : void
+    {
+        $heap = new Heap();
+        $heap->push(1);
+        $heap->push(3);
+        $heap->push(1);
+        $heap->push(4);
+
+        self::assertEquals([1, 1, 3], $heap->getNSmallest(3));
+    }
+
+    public function testNLargest(): void
+    {
+        $heap = new Heap();
+        $heap->push(1);
+        $heap->push(3);
+        $heap->push(1);
+        $heap->push(4);
+        $heap->push(4);
+
+        self::assertEquals([4, 4, 3], $heap->getNLargest(3));
+    }
+
+    public function testSize(): void
+    {
+        $heap = new Heap();
+        for ($i = 1; $i < 6; ++$i) {
+            $heap->push($i);
+        }
+
+        self::assertEquals(5, $heap->size());
+    }
+
+    public function testClear(): void
+    {
+        $heap = new Heap();
+        for ($i = 1; $i < 6; ++$i) {
+            $heap->push($i);
+        }
+
+        $heap->clear();
+        self::assertEquals(0, $heap->size());
+    }
+
+    public function testEmpty(): void
+    {
+        $heap = new Heap();
+        self::assertTrue($heap->empty());
+
+        for ($i = 1; $i < 6; ++$i) {
+            $heap->push($i);
+        }
+
+        self::assertFalse($heap->empty());
+    }
+}
\ No newline at end of file