Add Cluster tests (#254)

src/Clustering/KMeans/Cluster.php

@@ -49,7 +49,7 @@ class Cluster extends Point implements IteratorAggregate, Countable
     public function attach(Point $point): Point
     {
         if ($point instanceof self) {
-            throw new LogicException('cannot attach a cluster to another');
+            throw new LogicException('Cannot attach a cluster to another');
         }
 
         $this->points->attach($point);

tests/Clustering/KMeans/ClusterTest.php

@@ -0,0 +1,49 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Phpml\Tests\Clustering\KMeans;
+
+use LogicException;
+use Phpml\Clustering\KMeans\Cluster;
+use Phpml\Clustering\KMeans\Point;
+use Phpml\Clustering\KMeans\Space;
+use PHPUnit\Framework\TestCase;
+
+class ClusterTest extends TestCase
+{
+    public function testThrowExceptionWhenAttachingToCluster(): void
+    {
+        $this->expectException(LogicException::class);
+        $this->expectExceptionMessage('Cannot attach a cluster to another');
+
+        $cluster = new Cluster(new Space(1), []);
+        $cluster->attach(clone $cluster);
+    }
+
+    public function testToArray(): void
+    {
+        $cluster = new Cluster(new Space(2), [1, 2]);
+        $cluster->attach(new Point([1, 1]));
+
+        $this->assertSame([
+            'centroid' => [1, 2],
+            'points' => [
+                [1, 1],
+            ],
+        ], $cluster->toArray());
+    }
+
+    public function testDetach(): void
+    {
+        $cluster = new Cluster(new Space(2), []);
+        $cluster->attach(new Point([1, 2]));
+        $cluster->attach($point = new Point([1, 1]));
+
+        $detachedPoint = $cluster->detach($point);
+
+        $this->assertSame($detachedPoint, $point);
+        $this->assertNotContains($point, $cluster->getPoints());
+        $this->assertCount(1, $cluster);
+    }
+}