create-singleton-design-pattern

Author: git-growthdev

composer.json

@@ -14,6 +14,11 @@
             "Growthdev\\DesignPatterns\\": "src/"
         }
     },
+    "autoload-dev": {
+        "psr-4": {
+            "Growthdev\\DesignPatterns\\Tests\\": "tests/"
+        }
+    },
     "authors": [
         {
             "name": "Walmir Silva",

src/Creational/Singleton/Singleton.php

@@ -0,0 +1,35 @@
+<?php
+
+declare(strict_types=1);
+
+namespace DesignPatterns\Creational\Singleton;
+
+final class Singleton
+{
+    private static ?Singleton $instance = null;
+
+    public static function getInstance(): Singleton
+    {
+        if (null === static::$instance) {
+            static::$instance = new static();
+        }
+
+        return static::$instance;
+    }
+
+    protected function __construct()
+    {
+    }
+
+    private function __clone()
+    {
+    }
+
+    private function __wakeup()
+    {
+    }
+
+    private function __sleep()
+    {
+    }
+}

tests/Creational/Singleton/SingletonTest.php

@@ -0,0 +1,42 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Growthdev\DesignPatterns\Creational\Singleton;
+
+use DesignPatterns\Creational\Singleton\Singleton;
+use PHPUnit\Framework\TestCase;
+
+final class SingletonTest extends TestCase
+{
+  public function testShoudBeTheSameInstanceForTwoObjets(): void
+  {
+    $firstInstance = Singleton::getInstance();
+    $secondInstance = SingleTon::getInstance();
+
+    $this->assertSame($firstInstance, $secondInstance);
+  }
+
+  public function testThrowErrorWhenTryToCreateInstance(): void
+  {
+    $this->expectException(Error::class);
+
+    $instance = new Singleton();
+  }
+
+  public function testThrowExceptionWhenTryToClone(): void
+  {
+    $this->expectException(Error::class);
+
+    $instance = Singleton::getInstance();
+    $clone = clone $instance;
+  }
+
+  public function testThrowExceptionWhenTryToSerialize(): void
+  {
+    $this->expectException(Error::class);
+
+    $instance = Singleton::getInstance();
+    $serialize = serialize($instance);
+  }
+}