diff --git a/Algorithm/Frequency/Apriori.php b/Algorithm/Frequency/Apriori.php
index 93f547b3c..3a2063c0f 100644
--- a/Algorithm/Frequency/Apriori.php
+++ b/Algorithm/Frequency/Apriori.php
@@ -70,8 +70,8 @@ final class Apriori
      *
      * The algorithm cheks how often a set exists in a given set of sets.
      *
-     * @param array<array> $sets   Sets of a set (e.g. [[1,2,3,4], [1,2], [1]])
-     * @param array        $subset Subset to check for (empty array -> all subsets are checked)
+     * @param array<string[]> $sets   Sets of a set (e.g. [[1,2,3,4], [1,2], [1]])
+     * @param string[]        $subset Subset to check for (empty array -> all subsets are checked)
      *
      * @return array
      *
diff --git a/Business/Recommendation/MemoryCF.php b/Business/Recommendation/MemoryCF.php
index c81ac3a1e..972511543 100644
--- a/Business/Recommendation/MemoryCF.php
+++ b/Business/Recommendation/MemoryCF.php
@@ -189,11 +189,9 @@ final class MemoryCF
         $anglePointer    = \array_keys($cosine);
 
         // Inspect items of the top n comparable users
-        for ($i = 1; $i <= $size; ++$i) {
-            $index = (int) ($i / 2) - 1;
-
-            $uId       = $i % 2 === 1 ? $distancePointer[$index] : $anglePointer[$index];
-            $distances = $i % 2 === 1 ? $euclidean : $cosine;
+        for ($i = 0; $i < $size; ++$i) {
+            $uId       = $i % 2 === 0 ? $distancePointer[$i] : $anglePointer[$i];
+            $distances = $i % 2 === 0 ? $euclidean : $cosine;
 
             foreach ($this->rankings[$uId] as $iId => $_) {
                 // Item is not already in dataset and not in historic dataset (we are only interested in new)
diff --git a/tests/Algorithm/Frequency/AprioriTest.php b/tests/Algorithm/Frequency/AprioriTest.php
index 9bfc8a44c..7501f6b5a 100644
--- a/tests/Algorithm/Frequency/AprioriTest.php
+++ b/tests/Algorithm/Frequency/AprioriTest.php
@@ -54,14 +54,30 @@ final class AprioriTest extends \PHPUnit\Framework\TestCase
         );
 
         self::assertEquals(
-            [],
+            [
+                '4' => 5,
+                '3' => 3,
+                '3:4' => 3,
+                '2' => 5,
+                '2:4' => 4,
+                '2:3' => 2,
+                '2:3:4' => 2,
+                '1' => 3,
+                '1:4' => 2,
+                '1:3' => 1,
+                '1:3:4' => 1,
+                '1:2' => 3,
+                '1:2:4' => 2,
+                '1:2:3' => 1,
+                '1:2:3:4' => 1,
+            ],
             Apriori::apriori([
-                [1, 2, 3, 4],
-                [1, 2, 4],
-                [1, 2],
-                [2, 3, 4],
-                [3, 4],
-                [2, 4],
+                ['1', '2', '3', '4'],
+                ['1', '2', '4'],
+                ['1', '2'],
+                ['2', '3', '4'],
+                ['3', '4'],
+                ['2', '4'],
             ])
         );
     }
@@ -85,14 +101,14 @@ final class AprioriTest extends \PHPUnit\Framework\TestCase
             ['2:3' => 2],
             Apriori::apriori(
                 [
-                    [1, 2, 3, 4],
-                    [1, 2, 4],
-                    [1, 2],
-                    [2, 3, 4],
-                    [3, 4],
-                    [2, 4],
+                    ['1', '2', '3', '4'],
+                    ['1', '2', '4'],
+                    ['1', '2'],
+                    ['2', '3', '4'],
+                    ['3', '4'],
+                    ['2', '4'],
                 ],
-                [2, 3]
+                ['2', '3']
             )
         );
     }
diff --git a/tests/Algorithm/Graph/DependencyResolverTest.php b/tests/Algorithm/Graph/DependencyResolverTest.php
index 13ba3aed1..e6abf5832 100644
--- a/tests/Algorithm/Graph/DependencyResolverTest.php
+++ b/tests/Algorithm/Graph/DependencyResolverTest.php
@@ -26,17 +26,23 @@ require_once __DIR__ . '/../../Autoloader.php';
 final class DependencyResolverTest extends \PHPUnit\Framework\TestCase
 {
     /**
-     * @testdox A value is matched with the minimum quantity of available coins.
+     * @covers phpOMS\Algorithm\Graph\DependencyResolver
+     * @group framework
+     */
+    public function testResolveCircular() : void
+    {
+        self::assertEquals(
+            null,
+            DependencyResolver::resolve([0 => [1, 2], 1 => [0, 2], 2 => []])
+        );
+    }
+
+    /**
      * @covers phpOMS\Algorithm\Graph\DependencyResolver
      * @group framework
      */
     public function testResolve() : void
     {
-        self::assertEquals(
-            null,
-            DependencyResolver::resolve([0 => [1, 2], 1 => [0, 2], 2 => []])
-        );
-
         self::assertEquals(
             [0, 1, 2, 3],
             DependencyResolver::resolve([0 => [1, 2], 1 => [2, 3], 2 => [], 3 => []])
diff --git a/tests/DataStorage/Database/TestModel/BaseModelMapper.php b/tests/DataStorage/Database/TestModel/BaseModelMapper.php
index f70e01dc1..7ef5c61d4 100755
--- a/tests/DataStorage/Database/TestModel/BaseModelMapper.php
+++ b/tests/DataStorage/Database/TestModel/BaseModelMapper.php
@@ -54,10 +54,12 @@ class BaseModelMapper extends DataMapperFactory
         'belongsToOne' => [
             'mapper'   => BelongsToModelMapper::class,
             'external' => 'test_base_belongs_to_one',
+            'private'  => true,
         ],
         'belongsToOnePrivate' => [
             'mapper'   => BelongsToModelMapper::class,
             'external' => 'test_base_belongs_to_one',
+            'private'  => true,
         ],
     ];