Increase Mutation Score Indicator (MSI) by creating stronger tests of BaseCollection class

tests/Collection/BaseCollection/User.php

@@ -0,0 +1,45 @@
+<?php
+
+/**
+ * (c) Meritoo.pl, http://www.meritoo.pl
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+declare(strict_types=1);
+
+namespace Meritoo\Test\Common\Collection\BaseCollection;
+
+/**
+ * User. Element of collection.
+ *
+ * @author    Meritoo <github@meritoo.pl>
+ * @copyright Meritoo <http://www.meritoo.pl>
+ *
+ * @internal
+ * @coversNothing
+ */
+final class User
+{
+    /** @var string */
+    private $firstName;
+
+    /** @var string */
+    private $lastName;
+
+    public function __construct(string $firstName, string $lastName)
+    {
+        $this->firstName = $firstName;
+        $this->lastName = $lastName;
+    }
+
+    public function getFirstName(): string
+    {
+        return $this->firstName;
+    }
+
+    public function getLastName(): string
+    {
+        return $this->lastName;
+    }
+}