Added small tests for default values (#275)

* Added small tests for default values

* Added more tests

* cs

Author: Nyholm

tests/Unit/ConfigurationTest.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace AsyncAws\Core\Tests\Unit;
+
+use AsyncAws\Core\Configuration;
+use PHPUnit\Framework\TestCase;
+
+class ConfigurationTest extends TestCase
+{
+    public function testDefaultValues()
+    {
+        $config = Configuration::create(['endpoint' => 'foo']);
+        self::assertEquals('foo', $config->get('endpoint'));
+
+        $config = Configuration::create(['endpoint' => '']);
+        self::assertEquals('', $config->get('endpoint'));
+
+        $config = Configuration::create([]);
+        self::assertEquals('https://%service%.%region%.amazonaws.com', $config->get('endpoint'));
+
+        // If a configuration value is set to null, we should use default value.
+        $config = Configuration::create(['endpoint' => null]);
+        self::assertEquals('https://%service%.%region%.amazonaws.com', $config->get('endpoint'));
+
+        $config = Configuration::create([]);
+        self::assertEquals('default', $config->get('profile'));
+
+        putenv('AWS_PROFILE=foo');
+        $config = Configuration::create([]);
+        self::assertEquals('foo', $config->get('profile'));
+
+        putenv('AWS_PROFILE');
+        $config = Configuration::create([]);
+        self::assertEquals('default', $config->get('profile'));
+    }
+}