Add atomic counter test

Server/AtomicCounterTest.php

@@ -0,0 +1,53 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Tests\Bundle\SwooleBundle\Server;
+
+use App\Bundle\SwooleBundle\Server\AtomicCounter;
+use Generator;
+use PHPUnit\Framework\TestCase;
+
+class AtomicCounterTest extends TestCase
+{
+    public function testCreateCounter(): void
+    {
+        $counter = AtomicCounter::fromZero();
+
+        $this->assertSame(0, $counter->get());
+    }
+
+    public function countProvider(): Generator
+    {
+        return $this->generateArrays(0, 999, 65563);
+    }
+
+    /**
+     * @dataProvider countProvider
+     *
+     * @param int $count
+     */
+    public function testSingleThreadedCounting(int $count): void
+    {
+        $counter = AtomicCounter::fromZero();
+
+        $this->incrementCounter($counter, $count);
+
+        $this->assertSame($count, $counter->get());
+    }
+
+    private function generateArrays(...$values): Generator
+    {
+        foreach ($values as $value) {
+            yield [$value];
+        }
+    }
+
+    private function incrementCounter(AtomicCounter $counter, int $times): void
+    {
+        while ($times > 0) {
+            $counter->increment();
+            --$times;
+        }
+    }
+}