diff --git a/src/Model/Prompt/PromptTemplate.php b/src/Model/Prompt/PromptTemplate.php
index e3ad65d..e198555 100644
--- a/src/Model/Prompt/PromptTemplate.php
+++ b/src/Model/Prompt/PromptTemplate.php
@@ -23,7 +23,7 @@
  */
 final class PromptTemplate implements \Stringable
 {
-    private readonly string $template;
+    private string $template;
 
     private ?string $prompt = null;
 
diff --git a/src/Retrieval/Loader/Directory/DirectoryLoader.php b/src/Retrieval/Loader/Directory/DirectoryLoader.php
index b70e91c..f4604c5 100644
--- a/src/Retrieval/Loader/Directory/DirectoryLoader.php
+++ b/src/Retrieval/Loader/Directory/DirectoryLoader.php
@@ -64,7 +64,7 @@ public function load(AbstractReader $reader = new FileReader()): iterable
     public function loadAndSplit(SplitterInterface $splitter, AbstractReader $reader = new FileReader()): iterable
     {
         foreach ($this->load($reader) as $document) {
-            yield from $splitter->splitDocuments($document);
+            yield from $splitter->splitDocument($document);
         }
     }
 }
diff --git a/src/Retrieval/Splitter/SplitterInterface.php b/src/Retrieval/Splitter/SplitterInterface.php
index da1cdf0..5f7e62e 100644
--- a/src/Retrieval/Splitter/SplitterInterface.php
+++ b/src/Retrieval/Splitter/SplitterInterface.php
@@ -28,7 +28,8 @@ interface SplitterInterface
     public function splitText(string $text): iterable;
 
     /**
-     * @return iterable<Document>
+     * @param iterable<int, string> $splits
+     * @return iterable<int, Document>
      */
     public function createDocuments(iterable $splits): iterable;
 
diff --git a/src/Retrieval/Splitter/TextSplitter.php b/src/Retrieval/Splitter/TextSplitter.php
index b2f14d5..8357167 100644
--- a/src/Retrieval/Splitter/TextSplitter.php
+++ b/src/Retrieval/Splitter/TextSplitter.php
@@ -92,7 +92,7 @@ public function createDocuments(iterable $splits): iterable
     {
         foreach ($splits as $index => $chunk) {
             yield new Document($chunk, metadata: new Metadata(
-                hash: md5((string) $chunk),
+                hash: md5($chunk),
                 chunkNumber: $index
             ));
         }
diff --git a/tests/Retrieval/VectorStore/DistanceTest.php b/tests/Retrieval/VectorStore/DistanceTest.php
new file mode 100644
index 0000000..a0142e6
--- /dev/null
+++ b/tests/Retrieval/VectorStore/DistanceTest.php
@@ -0,0 +1,61 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Devscast\Lugha\Tests\Retrieval\VectorStore;
+
+use PHPUnit\Framework\TestCase;
+use Devscast\Lugha\Retrieval\VectorStore\Distance;
+
+/**
+ * Class DistanceTest.
+ *
+ * @author bernard-ng <bernard@devscast.tech>
+ */
+final class DistanceTest extends TestCase
+{
+    public function testVectorWithDifferentDimensions(): void
+    {
+        $this->expectException(\InvalidArgumentException::class);
+        $this->expectExceptionMessage('Vectors must have the same dimension.');
+
+        $distance = Distance::COSINE;
+        $a = [2, 4, 1, 3];
+        $b = [3, 5, 2];
+
+        $distance->compute($a, $b);
+    }
+
+    public function testDifferentVectorDistances(): void
+    {
+        $a = [2, 4, 1, 3];
+        $b = [3, 5, 2, 1];
+        
+        $this->assertEquals(0.0937, round(Distance::COSINE->compute($a, $b), 4));
+        $this->assertEquals(2.6458, round(Distance::L2->compute($a, $b), 4));
+        $this->assertEquals(5.0, round(Distance::L1->compute($a, $b), 4));
+        $this->assertEquals(31.0, round(Distance::INNER_PRODUCT->compute($a, $b), 4));
+    }
+
+    public function testSimilarVectorDistances(): void
+    {
+        $a = [2, 4, 1, 3];
+        $b = [2, 4, 1, 2];
+
+        $this->assertEquals(0.0141, round(Distance::COSINE->compute($a, $b), 4));
+        $this->assertEquals(1.0, round(Distance::L2->compute($a, $b), 4));
+        $this->assertEquals(1.0, round(Distance::L1->compute($a, $b), 4));
+        $this->assertEquals(27.0, round(Distance::INNER_PRODUCT->compute($a, $b), 4));
+    }
+
+    public function testSameVectorDistances(): void
+    {
+        $a = [2, 4, 1, 3];
+        $b = [2, 4, 1, 3];
+
+        $this->assertEquals(0.0, round(Distance::COSINE->compute($a, $b), 4));
+        $this->assertEquals(0.0, round(Distance::L2->compute($a, $b), 4));
+        $this->assertEquals(0.0, round(Distance::L1->compute($a, $b), 4));
+        $this->assertEquals(30.0, round(Distance::INNER_PRODUCT->compute($a, $b), 4));
+    }
+}