Added tests for the Arr::first() method

tests/Arr/FirstTest.php

@@ -0,0 +1,33 @@
+<?php
+
+namespace Yetii\Tests\Arr;
+
+use PHPUnit\Framework\TestCase;
+use YeTii\General\Arr;
+
+/**
+ * Class FirstTest
+ */
+class FirstTest extends TestCase
+{
+    /**
+     * @var array
+     */
+    public $testData = [
+        'apples',
+        'oranges',
+        'apples',
+    ];
+
+    /**
+     * Test whether it shifts the first element off the array and returns this
+     */
+    public function testCanGetFirstArrayElement()
+    {
+        $array = new Arr($this->testData);
+        $result = $array->first();
+
+        $this->assertTrue($result === ['apples']);
+        $this->assertTrue($array->toArray() === ['oranges', 'apples']);
+    }
+}