diff --git a/Algorithm/Frequency/Apriori.php b/Algorithm/Frequency/Apriori.php
index 1df6b1c02..93f547b3c 100644
--- a/Algorithm/Frequency/Apriori.php
+++ b/Algorithm/Frequency/Apriori.php
@@ -91,6 +91,7 @@ final class Apriori
 
         $totalSet = \array_unique($totalSet);
         \sort($totalSet);
+        \sort($subset);
 
         // Combinations of items
         $combinations = self::generateSubsets($totalSet);
@@ -99,6 +100,10 @@ final class Apriori
         $table = [];
         foreach ($combinations as &$c) {
             \sort($c);
+            if (!empty($subset) && $c !== $subset) {
+                continue;
+            }
+
             $table[\implode(':', $c)] = 0;
         }
 
diff --git a/Business/Recommendation/MemoryCF.php b/Business/Recommendation/MemoryCF.php
index d66be710e..c81ac3a1e 100644
--- a/Business/Recommendation/MemoryCF.php
+++ b/Business/Recommendation/MemoryCF.php
@@ -87,7 +87,7 @@ final class MemoryCF
      *
      * @since 1.0.0
      */
-    public function euclideanDistance(array $ranking, array $rankings) : array
+    private function euclideanDistance(array $ranking, array $rankings) : array
     {
         $distances = [];
         foreach ($rankings as $idx => $r) {
@@ -107,7 +107,7 @@ final class MemoryCF
      *
      * @since 1.0.0
      */
-    public function cosineDistance(array $ranking, array $rankings) : array
+    private function cosineDistance(array $ranking, array $rankings) : array
     {
         $distances = [];
         foreach ($rankings as $idx => $r) {
diff --git a/tests/Algorithm/Frequency/AprioriTest.php b/tests/Algorithm/Frequency/AprioriTest.php
index 61e53d164..9bfc8a44c 100644
--- a/tests/Algorithm/Frequency/AprioriTest.php
+++ b/tests/Algorithm/Frequency/AprioriTest.php
@@ -28,7 +28,23 @@ final class AprioriTest extends \PHPUnit\Framework\TestCase
     public function testApriori() : void
     {
         self::assertEquals(
-            [],
+            [
+                'theta' => 2,
+                'epsilon' => 2,
+                'epsilon:theta' => 0,
+                'beta' => 4,
+                'beta:theta' => 2,
+                'beta:epsilon' => 2,
+                'beta:epsilon:theta' => 0,
+                'alpha' => 4,
+                'alpha:theta' => 2,
+                'alpha:epsilon' => 2,
+                'alpha:epsilon:theta' => 0,
+                'alpha:beta' => 4,
+                'alpha:beta:theta' => 2,
+                'alpha:beta:epsilon' => 2,
+                'alpha:beta:epsilon:theta' => 0,
+            ],
             Apriori::apriori([
                 ['alpha', 'beta', 'epsilon'],
                 ['alpha', 'beta', 'theta'],
diff --git a/tests/Algorithm/Graph/DependencyResolverTest.php b/tests/Algorithm/Graph/DependencyResolverTest.php
index bf1df2ab6..13ba3aed1 100644
--- a/tests/Algorithm/Graph/DependencyResolverTest.php
+++ b/tests/Algorithm/Graph/DependencyResolverTest.php
@@ -34,12 +34,12 @@ final class DependencyResolverTest extends \PHPUnit\Framework\TestCase
     {
         self::assertEquals(
             null,
-            DependencyResolver::resolve([0 => [1, 2], 1 => [0, 2]])
+            DependencyResolver::resolve([0 => [1, 2], 1 => [0, 2], 2 => []])
         );
 
         self::assertEquals(
             [0, 1, 2, 3],
-            DependencyResolver::resolve([0 => [1, 2], 1 => [2, 3]])
+            DependencyResolver::resolve([0 => [1, 2], 1 => [2, 3], 2 => [], 3 => []])
         );
     }
 }
diff --git a/tests/Algorithm/Graph/MarkovChainTest.php b/tests/Algorithm/Graph/MarkovChainTest.php
index 1733543bd..0521dc2d5 100644
--- a/tests/Algorithm/Graph/MarkovChainTest.php
+++ b/tests/Algorithm/Graph/MarkovChainTest.php
@@ -61,7 +61,7 @@ final class MarkovChainTest extends \PHPUnit\Framework\TestCase
      */
     public function testStepProbability() : void
     {
-        $markov = new MarkovChain();
+        $markov = new MarkovChain(2);
         $markov->setTraining(
             [
                 'A A' => ['A' => 0.18, 'D' => 0.6, 'G' => 0.22],
@@ -85,7 +85,7 @@ final class MarkovChainTest extends \PHPUnit\Framework\TestCase
      */
     public function testPathProbability() : void
     {
-        $markov = new MarkovChain();
+        $markov = new MarkovChain(2);
         $markov->setTraining(
             [
                 'A A' => ['A' => 0.18, 'D' => 0.6, 'G' => 0.22],
diff --git a/tests/Business/Recommendation/BayesianPersonalizedRankingTest.php b/tests/Business/Recommendation/BayesianPersonalizedRankingTest.php
new file mode 100644
index 000000000..880c78a1c
--- /dev/null
+++ b/tests/Business/Recommendation/BayesianPersonalizedRankingTest.php
@@ -0,0 +1,26 @@
+<?php
+/**
+ * Jingga
+ *
+ * PHP Version 8.1
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 2.0
+ * @version   1.0.0
+ * @link      https://jingga.app
+ */
+declare(strict_types=1);
+
+namespace phpOMS\tests\Business\Recommendation;
+
+use phpOMS\Business\Recommendation\BayesianPersonalizedRanking;
+
+/**
+ * @testdox phpOMS\tests\Business\Recommendation\BayesianPersonalizedRankingTest: Article affinity/correlation
+ *
+ * @internal
+ */
+final class BayesianPersonalizedRankingTest extends \PHPUnit\Framework\TestCase
+{
+}
diff --git a/tests/Business/Recommendation/MemoryCFTest.php b/tests/Business/Recommendation/MemoryCFTest.php
new file mode 100644
index 000000000..9308e7309
--- /dev/null
+++ b/tests/Business/Recommendation/MemoryCFTest.php
@@ -0,0 +1,40 @@
+<?php
+/**
+ * Jingga
+ *
+ * PHP Version 8.1
+ *
+ * @package   tests
+ * @copyright Dennis Eichhorn
+ * @license   OMS License 2.0
+ * @version   1.0.0
+ * @link      https://jingga.app
+ */
+declare(strict_types=1);
+
+namespace phpOMS\tests\Business\Recommendation;
+
+use phpOMS\Business\Recommendation\MemoryCF;
+
+/**
+ * @testdox phpOMS\tests\Business\Recommendation\MemoryCFTest: Article affinity/correlation
+ *
+ * @internal
+ */
+final class MemoryCFTest extends \PHPUnit\Framework\TestCase
+{
+    public function testBestMatch() : void
+    {
+        $memory = new MemoryCF([
+            'A' => [1.0, 2.0],
+            'B' => [2.0, 4.0],
+            'C' => [2.5, 4.0],
+            'D' => [4.5, 5.0],
+        ]);
+
+        self::assertEquals(
+            ['B', 'C'],
+            $memory->bestMatch([2.2, 4.1], 2)
+        );
+    }
+}
diff --git a/tests/DataStorage/Database/DataMapperAbstractTest.php b/tests/DataStorage/Database/DataMapperAbstractTest.php
index e9710625e..ea2afe43a 100755
--- a/tests/DataStorage/Database/DataMapperAbstractTest.php
+++ b/tests/DataStorage/Database/DataMapperAbstractTest.php
@@ -247,7 +247,10 @@ final class DataMapperAbstractTest extends \PHPUnit\Framework\TestCase
     public function testGetYield() : void
     {
         BaseModelMapper::create()->execute($this->model);
-        self::assertCount(1, BaseModelMapper::yield()->execute());
+
+        foreach (BaseModelMapper::yield()->execute() as $model) {
+            self::assertGreaterThan(0, $model->id);
+        }
     }
 
     public function testGetFor() : void
@@ -281,6 +284,7 @@ final class DataMapperAbstractTest extends \PHPUnit\Framework\TestCase
         $model1           = new BaseModel();
         $model1->datetime = new \DateTime('now');
         $id1              = BaseModelMapper::create()->execute($model1);
+
         \sleep(1);
         $model2           = new BaseModel();
         $model2->datetime = new \DateTime('now');