Update composer dependencies

composer.json

@@ -22,10 +22,10 @@
         "ext-mbstring": "*"
     },
     "require-dev": {
-        "phpunit/phpunit": "~4.8",
-        "satooshi/php-coveralls": "~1.0",
-        "squizlabs/php_codesniffer": "~2.6",
-        "friendsofphp/php-cs-fixer": "~1.12"
+        "phpunit/phpunit" : "^7.0",
+        "satooshi/php-coveralls": "~2.2",
+        "squizlabs/php_codesniffer": "~3.5",
+        "friendsofphp/php-cs-fixer": "~2.16"
     },
     "autoload": {
         "psr-4": { "jards\\gcsjardsapiclient\\Swagger\\Client\\" : "lib/" }

test/Api/FilesApiTest.php

@@ -41,7 +41,7 @@ use \jards\gcsjardsapiclient\Swagger\Client\ObjectSerializer;
  * @author   Swagger Codegen team
  * @link     https://github.com/swagger-api/swagger-codegen
  */
-class FilesApiTest extends \PHPUnit_Framework_TestCase
+class FilesApiTest extends \PHPUnit\Framework\TestCase
 {
 
     /**