Last try for prefer-lowest

.gitignore

@@ -1,3 +1,4 @@
 composer.lock
 vendor/
 bin/
+phpunit.xml

composer.json

@@ -12,7 +12,7 @@
         "symfony/asset": "^2.8|^3.0|^4.0",
         "symfony/browser-kit": "^2.8|^3.0|^4.0",
         "symfony/css-selector": "^2.3|^3.0|^4.0",
-        "symfony/swiftmailer-bundle": "^2.5|^3.0",
+        "symfony/swiftmailer-bundle": "^2.6|^3.0",
         "symfony/templating": "^2.8|^3.0|^4.0",
         "symfony/twig-bundle": "^2.8|^3.0|^4.0",
         "twilio/sdk": "^5.0"

phpunit.xml.dist

@@ -0,0 +1,25 @@
+<?xml version="1.0" encoding="UTF-8"?>
+
+<!-- https://phpunit.de/manual/current/en/appendixes.configuration.html -->
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+         xsi:noNamespaceSchemaLocation="http://schema.phpunit.de/6.5/phpunit.xsd"
+         backupGlobals="false"
+         colors="true"
+         bootstrap="bootstrap.php"
+>
+    <php>
+        <ini name="error_reporting" value="-1" />
+    </php>
+
+    <testsuites>
+        <testsuite name="NotifireBundle Test Suite">
+            <directory>tests/</directory>
+        </testsuite>
+    </testsuites>
+
+    <filter>
+        <whitelist>
+            <directory>src/</directory>
+        </whitelist>
+    </filter>
+</phpunit>