Add some semblance of testing.

composer.json

@@ -14,11 +14,17 @@
     },
     "require-dev": {
         "phpro/grumphp": "^0.15.0",
-        "friendsofphp/php-cs-fixer": "^2.14"
+        "friendsofphp/php-cs-fixer": "^2.14",
+        "phpunit/phpunit": "^8.0"
     },
     "autoload": {
         "psr-4": {
             "FooBar\\": "src/"
         }
+    },
+    "autoload-dev": {
+        "psr-4": {
+            "FooBar\\tests\\": "tests"
+        }
     }
 }

grumphp.yml

@@ -4,3 +4,4 @@ parameters:
   tasks:
     phpcsfixer2:
       config: .php_cs
+    phpunit: ~

phpunit.xml

@@ -0,0 +1,8 @@
+<?xml version="1.0" encoding="UTF-8" ?>
+<phpunit
+        xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+        xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/6.3/phpunit.xsd">
+    <testsuite name="main">
+        <directory>tests</directory>
+    </testsuite>
+</phpunit>

tests/ConfigurationTest.php

@@ -0,0 +1,29 @@
+<?php
+
+namespace tests\FooBar;
+
+use FooBar\Configuration;
+use PHPUnit\Framework\TestCase;
+
+class ConfigurationTest extends TestCase
+{
+    public function testDefaultSecurity()
+    {
+        $config = $this->getSampleConfig();
+
+        $this->assertTrue($config->isAuthorized('127.0.0.1'));
+        $this->assertFalse($config->isAuthorized('8.8.8.8'));
+    }
+
+    public function testLoadConfig()
+    {
+        $this->assertNotNull(Configuration::loadConfig());
+    }
+
+    private function getSampleConfig(): Configuration
+    {
+        $path = dirname(__DIR__) . '/config/config.sample.php';
+
+        return new Configuration(require $path);
+    }
+}