diff --git a/Stdlib/Map/MultiMap.php b/Stdlib/Map/MultiMap.php
index a0b4001d7..048547e68 100644
--- a/Stdlib/Map/MultiMap.php
+++ b/Stdlib/Map/MultiMap.php
@@ -90,7 +90,7 @@ class MultiMap implements \Countable
         $inserted = false;
 
         if ($this->keyType !== KeyType::SINGLE) {
-            $keys = [implode(':', $keys)];
+            $keys = [\implode(':', $keys)];
         }
 
         foreach ($keys as $key) {
@@ -202,7 +202,7 @@ class MultiMap implements \Countable
     {
         if (\is_array($key)) {
             if ($this->orderType === OrderType::LOOSE) {
-                $keys = Permutation::permut($key);
+                $keys = Permutation::permut($key, [], false);
 
                 foreach ($keys as $key => $value) {
                     $key = \implode(':', $value);
@@ -231,7 +231,7 @@ class MultiMap implements \Countable
      */
     public function set($key, $value) : bool
     {
-        if ($this->keyType === KeyType::MULTIPLE && is_array($key)) {
+        if ($this->keyType === KeyType::MULTIPLE && \is_array($key)) {
             return $this->setMultiple($key, $value);
         }
 
@@ -250,19 +250,17 @@ class MultiMap implements \Countable
      */
     private function setMultiple($key, $value) : bool
     {
-        if ($this->orderType !== OrderType::LOOSE) {
-            $permutation = Permutation::permut($key);
+        if ($this->orderType !== OrderType::STRICT) {
+            $permutation = Permutation::permut($key, [], false);
 
             foreach ($permutation as $permut) {
-                if ($this->set(implode(':', $permut), $value)) {
+                if ($this->set(\implode(':', $permut), $value)) {
                     return true;
                 }
             }
         } else {
-            return $this->set(implode(':', $key), $value);
+            return $this->set(\implode(':', $key), $value);
         }
-
-        return false;
     }
 
     /**
@@ -297,7 +295,7 @@ class MultiMap implements \Countable
      */
     public function remove($key) : bool
     {
-        if ($this->keyType === KeyType::MULTIPLE && is_array($key)) {
+        if ($this->keyType === KeyType::MULTIPLE && \is_array($key)) {
             return $this->removeMultiple($key);
         }
 
@@ -316,17 +314,17 @@ class MultiMap implements \Countable
     private function removeMultiple($key) : bool
     {
         if ($this->orderType !== OrderType::LOOSE) {
-            return $this->remove(implode(':', $key));
+            return $this->remove(\implode(':', $key));
         }
 
-        $keys  = Permutation::permut($key);
-        $found = true;
+        $keys  = Permutation::permut($key, [], false);
+        $found = false;
 
         foreach ($keys as $key => $value) {
-            $allFound = $this->remove(implode(':', $value));
+            $allFound = $this->remove(\implode(':', $value));
 
-            if (!$allFound) {
-                $found = false;
+            if ($allFound) {
+                $found = true;
             }
         }
 
@@ -399,43 +397,11 @@ class MultiMap implements \Countable
      */
     public function removeKey($key) : bool
     {
-        if ($this->keyType === KeyType::MULTIPLE && is_array($key)) {
-            return $this->removeKeyMultiple($key);
-        } else {
-            return $this->removeKeySingle($key);
+        if ($this->keyType === KeyType::MULTIPLE) {
+            return false;
         }
-    }
 
-    /**
-     * Remove key.
-     *
-     * This only removes the value if no other key exists for this value.
-     *
-     * @param mixed $key Key used to identify value
-     *
-     * @return bool
-     *
-     * @since  1.0.0
-     */
-    private function removeKeyMultiple($key) : bool
-    {
-        if ($this->orderType === OrderType::LOOSE) {
-            $keys = Permutation::permut($key);
-
-            $removed = false;
-
-            foreach ($keys as $key => $value) {
-                $removed = $this->removeKey(implode(':', $value));
-
-                if (!$removed) {
-                    return false;
-                }
-            }
-
-            return $removed;
-        } else {
-            return $this->removeKey(implode(':', $key));
-        }
+        return $this->removeKeySingle($key);
     }
 
     /**
@@ -493,7 +459,9 @@ class MultiMap implements \Countable
     public function getSiblingsMultiple($key) : array
     {
         if ($this->orderType === OrderType::LOOSE) {
-            return Permutation::permut($key);
+            $key = \is_array($key) ? $key : [$key];
+
+            return Permutation::permut($key, [], false);
         }
 
         return [];
diff --git a/Utils/Permutation.php b/Utils/Permutation.php
index 80a629e35..fcfca34b8 100644
--- a/Utils/Permutation.php
+++ b/Utils/Permutation.php
@@ -45,12 +45,12 @@ final class Permutation
      *
      * @since  1.0.0
      */
-    public static function permut(array $toPermute, array $result = []) : array
+    public static function permut(array $toPermute, array $result = [], bool $concat = true) : array
     {
         $permutations = [];
 
         if (empty($toPermute)) {
-            $permutations[] = \implode('', $result);
+            $permutations[] = $concat ? \implode('', $result) : $result;
         } else {
             foreach ($toPermute as $key => $val) {
                 $newArr   = $toPermute;
@@ -59,7 +59,7 @@ final class Permutation
 
                 unset($newArr[$key]);
 
-                $permutations = array_merge($permutations, self::permut($newArr, $newres));
+                $permutations = \array_merge($permutations, self::permut($newArr, $newres, $concat));
             }
         }
 
@@ -78,7 +78,7 @@ final class Permutation
      */
     public static function isPermutation(string $a, string $b) : bool
     {
-        return count_chars($a, 1) === count_chars($b, 1);
+        return \count_chars($a, 1) === \count_chars($b, 1);
     }
 
     /**
@@ -93,7 +93,7 @@ final class Permutation
      */
     public static function isPalindrome(string $a, string $filter = 'a-zA-Z0-9') : bool
     {
-        $a = \strtolower(preg_replace('/[^' . $filter . ']/', '', $a));
+        $a = \strtolower(\preg_replace('/[^' . $filter . ']/', '', $a));
 
         return $a === \strrev($a);
     }
@@ -112,11 +112,11 @@ final class Permutation
      */
     public static function permutate($toPermute, array $key)
     {
-        if (!is_array($toPermute) && !is_string($toPermute)) {
+        if (!\is_array($toPermute) && !\is_string($toPermute)) {
             throw new \InvalidArgumentException('Parameter has to be array or string');
         }
 
-        $length = is_array($toPermute) ? \count($toPermute) : \strlen($toPermute);
+        $length = \is_array($toPermute) ? \count($toPermute) : \strlen($toPermute);
 
         if (\count($key) > $length) {
             throw new \InvalidArgumentException('There mustn not be more keys than permutation elements.');
diff --git a/tests/Stdlib/Map/MultiMapTest.php b/tests/Stdlib/Map/MultiMapTest.php
index a76b8484e..5c33d6b3e 100644
--- a/tests/Stdlib/Map/MultiMapTest.php
+++ b/tests/Stdlib/Map/MultiMapTest.php
@@ -14,6 +14,8 @@
 namespace phpOMS\tests\Stdlib\Map;
 
 use phpOMS\Stdlib\Map\MultiMap;
+use phpOMS\Stdlib\Map\KeyType;
+use phpOMS\Stdlib\Map\OrderType;
 
 class MultiMapTest extends \PHPUnit\Framework\TestCase
 {
@@ -43,7 +45,7 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertFalse($map->remove('someKey'));
     }
 
-    public function testBasicAdd()
+    public function testBasicAddAny()
     {
         $map = new MultiMap();
 
@@ -54,7 +56,7 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertEquals('val1', $map->get('b'));
     }
 
-    public function testOverwrite()
+    public function testOverwriteAny()
     {
         $map = new MultiMap();
 
@@ -66,7 +68,7 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertEquals('val2', $map->get('b'));
     }
 
-    public function testOverwritePartialFalse()
+    public function testOverwritePartialFalseAny()
     {
         $map = new MultiMap();
 
@@ -79,7 +81,7 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertEquals('val3', $map->get('c'));
     }
 
-    public function testOverwriteFalseFalse()
+    public function testOverwriteFalseFalseAny()
     {
         $map = new MultiMap();
 
@@ -93,7 +95,7 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertEquals('val3', $map->get('c'));
     }
 
-    public function testSet()
+    public function testSetAny()
     {
         $map = new MultiMap();
 
@@ -112,7 +114,7 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertEquals('val3', $map->get('c'));
     }
 
-    public function testRemap()
+    public function testRemapAny()
     {
         $map = new MultiMap();
 
@@ -142,7 +144,7 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertEquals('val3', $map->get('c'));
     }
 
-    public function testMapInfo()
+    public function testMapInfoAny()
     {
         $map = new MultiMap();
 
@@ -159,7 +161,7 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertTrue(\is_array($map->values()));
     }
 
-    public function testSiblings()
+    public function testSiblingsAny()
     {
         $map = new MultiMap();
 
@@ -177,7 +179,7 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertEquals(['a'], $siblings);
     }
 
-    public function testRemove()
+    public function testRemoveAny()
     {
         $map = new MultiMap();
 
@@ -190,9 +192,6 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         $removed = $map->remove('d');
         self::assertFalse($removed);
 
-        $removed = $map->remove('d');
-        self::assertFalse($removed);
-
         $removed = $map->remove('c');
         self::assertTrue($removed);
         self::assertEquals(2, \count($map->keys()));
@@ -206,4 +205,169 @@ class MultiMapTest extends \PHPUnit\Framework\TestCase
         self::assertEquals(1, \count($map->keys()));
         self::assertEquals(1, \count($map->values()));
     }
+
+    public function testBasicAddExact()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE);
+
+        $inserted = $map->add(['a', 'b'], 'val1');
+        self::assertEquals(1, $map->count());
+        self::assertTrue($inserted);
+        self::assertEquals('val1', $map->get(['a', 'b']));
+        self::assertEquals('val1', $map->get(['b', 'a']));
+    }
+
+    public function testBasicAddExactOrdered()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE, OrderType::STRICT);
+
+        $inserted = $map->add(['a', 'b'], 'val1');
+        self::assertEquals(1, $map->count());
+        self::assertTrue($inserted);
+        self::assertEquals('val1', $map->get(['a', 'b']));
+        self::assertEquals(null, $map->get(['b', 'a']));
+    }
+
+    public function testOverwriteExact()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE);
+
+        $inserted = $map->add(['a', 'b'], 'val1');
+        $inserted = $map->add(['a', 'b'], 'val2');
+        self::assertEquals(1, $map->count());
+        self::assertTrue($inserted);
+        self::assertEquals('val2', $map->get(['a', 'b']));
+    }
+
+    public function testOverwritePartialFalseExact()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE);
+
+        $inserted = $map->add(['a', 'b'], 'val2');
+        $inserted = $map->add(['a', 'c'], 'val3', false);
+        self::assertEquals(2, $map->count());
+        self::assertTrue($inserted);
+        self::assertEquals('val2', $map->get(['a', 'b']));
+        self::assertEquals('val3', $map->get(['c', 'a']));
+    }
+
+    public function testOverwriteFalseFalseExact()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE);
+
+        $inserted = $map->add(['a', 'b'], 'val2');
+        $inserted = $map->add(['a', 'c'], 'val3', false);
+        $inserted = $map->add(['a', 'c'], 'val4', false);
+        self::assertEquals(2, $map->count());
+        self::assertFalse($inserted);
+        self::assertEquals('val2', $map->get(['a', 'b']));
+        self::assertEquals('val3', $map->get(['a', 'c']));
+    }
+
+    public function testSetExact()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE);
+
+        $inserted = $map->add(['a', 'b'], 'val2');
+        $inserted = $map->add(['a', 'c'], 'val3', false);
+
+        $set = $map->set('d', 'val4');
+        self::assertFalse($set);
+        self::assertEquals(2, $map->count());
+
+        $set = $map->set(['a', 'b'], 'val4');
+        self::assertEquals(2, $map->count());
+        self::assertTrue($set);
+        self::assertEquals('val4', $map->get(['a', 'b']));
+        self::assertEquals('val4', $map->get(['b', 'a']));
+    }
+
+    public function testSetExactOrdered()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE, OrderType::STRICT);
+
+        $inserted = $map->add(['a', 'b'], 'val2');
+        $inserted = $map->add(['a', 'c'], 'val3', false);
+
+        $set = $map->set('c', 'val4');
+        self::assertFalse($set);
+        self::assertEquals(2, $map->count());
+
+        $set = $map->set(['a', 'b'], 'val4');
+        self::assertEquals(2, $map->count());
+        self::assertTrue($set);
+        self::assertEquals('val4', $map->get(['a', 'b']));
+
+        $set = $map->set(['b', 'a'], 'val5');
+        self::assertEquals(2, $map->count());
+        self::assertFalse($set);
+    }
+
+    public function testRemapExact()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE);
+
+        $inserted = $map->add(['a', 'b'], 'val2');
+        $remap    = $map->remap(['a', 'b'], ['c', 'd']);
+
+        self::assertFalse($remap);
+    }
+
+    public function testSiblingsExact()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE);
+
+        $inserted = $map->add(['a', 'b'], 'val2');
+        self::assertEquals([['a', 'b'], ['b', 'a']], $map->getSiblings(['a', 'b']));
+    }
+
+    public function testSiblingsExactOrdered()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE, OrderType::STRICT);
+
+        $inserted = $map->add(['a', 'b'], 'val2');
+        self::assertEquals([], $map->getSiblings(['a', 'b']));
+    }
+
+    public function testRemoveExact()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE);
+
+        $inserted = $map->add(['a', 'b'], 'val2');
+        $inserted = $map->add(['a', 'c'], 'val3', false);
+
+        self::assertEquals(2, \count($map->keys()));
+        self::assertEquals(2, \count($map->values()));
+
+        $removed = $map->remove('d');
+        self::assertFalse($removed);
+
+        $removed = $map->remove(['a', 'b']);
+        self::assertTrue($removed);
+        self::assertEquals(1, \count($map->keys()));
+        self::assertEquals(1, \count($map->values()));
+
+        self::assertFalse($map->removeKey(['a', 'b']));
+    }
+
+    public function testRemoveExactOrdered()
+    {
+        $map = new MultiMap(KeyType::MULTIPLE, OrderType::STRICT);
+
+        $inserted = $map->add(['a', 'b'], 'val2');
+        $inserted = $map->add(['a', 'c'], 'val3', false);
+
+        self::assertEquals(2, \count($map->keys()));
+        self::assertEquals(2, \count($map->values()));
+
+        $removed = $map->remove(['b', 'a']);
+        self::assertFalse($removed);
+
+        $removed = $map->remove(['a', 'b']);
+        self::assertTrue($removed);
+        self::assertEquals(1, \count($map->keys()));
+        self::assertEquals(1, \count($map->values()));
+
+        self::assertFalse($map->removeKey(['a', 'b']));
+    }
 }