Added more Rest module tests

module/Rest/test/ConfigProviderTest.php

@@ -0,0 +1,33 @@
+<?php
+namespace ShlinkioTest\Shlink\Rest;
+
+use PHPUnit_Framework_TestCase as TestCase;
+use Shlinkio\Shlink\Rest\ConfigProvider;
+
+class ConfigProviderTest extends TestCase
+{
+    /**
+     * @var ConfigProvider
+     */
+    protected $configProvider;
+
+    public function setUp()
+    {
+        $this->configProvider = new ConfigProvider();
+    }
+
+    /**
+     * @test
+     */
+    public function properConfigIsReturned()
+    {
+        $config = $this->configProvider->__invoke();
+
+        $this->assertArrayHasKey('error_handler', $config);
+        $this->assertArrayHasKey('middleware_pipeline', $config);
+        $this->assertArrayHasKey('rest', $config);
+        $this->assertArrayHasKey('routes', $config);
+        $this->assertArrayHasKey('services', $config);
+        $this->assertArrayHasKey('translator', $config);
+    }
+}