diff --git a/phpunit.xml.dist b/phpunit.xml.dist
index ac8970539..e0be34e2d 100644
--- a/phpunit.xml.dist
+++ b/phpunit.xml.dist
@@ -12,6 +12,11 @@
     <testsuites>
         <testsuite name="PHPMailerTests">
             <directory>./test/</directory>
+            <exclude>test/PHPMailer/AddAddressWithIDNTest.php</exclude>
+        </testsuite>
+        <!-- Separate group for tests which include the `fakefunctions.php` file as it can screw up other tests. -->
+        <testsuite name="PHPMailerWithFakedFunctionsTests">
+            <file>./test/PHPMailer/AddAddressWithIDNTest.php</file>
         </testsuite>
     </testsuites>
     <listeners>
diff --git a/test/PHPMailer/AddAddressWithIDNTest.php b/test/PHPMailer/AddAddressWithIDNTest.php
new file mode 100644
index 000000000..1dd06fef1
--- /dev/null
+++ b/test/PHPMailer/AddAddressWithIDNTest.php
@@ -0,0 +1,33 @@
+<?php
+
+/**
+ * PHPMailer - PHP email transport unit tests.
+ * PHP version 5.5.
+ *
+ * @author    Marcus Bointon <phpmailer@synchromedia.co.uk>
+ * @author    Andy Prevost
+ * @copyright 2012 - 2020 Marcus Bointon
+ * @copyright 2004 - 2009 Andy Prevost
+ * @license   https://www.gnu.org/licenses/old-licenses/lgpl-2.1.html GNU Lesser General Public License
+ */
+
+namespace PHPMailer\Test\PHPMailer;
+
+use PHPMailer\PHPMailer\PHPMailer;
+use PHPMailer\Test\TestCase;
+
+/**
+ * @covers \PHPMailer\PHPMailer\PHPMailer::addAddress
+ */
+final class AddAddressWithIDNTest extends TestCase
+{
+    public function testGivenIdnAddress_addAddress_returns_true()
+    {
+        if (file_exists(\PHPMAILER_INCLUDE_DIR . '/test/fakefunctions.php') === false) {
+            $this->markTestSkipped('/test/fakefunctions.php file not found');
+        }
+
+        include \PHPMAILER_INCLUDE_DIR . '/test/fakefunctions.php';
+        $this->assertTrue($this->Mail->addAddress('test@françois.ch'));
+    }
+}
diff --git a/test/PHPMailer/PHPMailerTest.php b/test/PHPMailer/PHPMailerTest.php
index 0b82fe125..dcf9d8266 100644
--- a/test/PHPMailer/PHPMailerTest.php
+++ b/test/PHPMailer/PHPMailerTest.php
@@ -1258,16 +1258,6 @@ public function testSmtpConnect()
         $this->Mail->smtpClose();
     }
 
-    public function testGivenIdnAddress_addAddress_returns_true()
-    {
-        if (file_exists(\PHPMAILER_INCLUDE_DIR . '/test/fakefunctions.php') === false) {
-            $this->markTestSkipped('/test/fakefunctions.php file not found');
-        }
-
-        include \PHPMAILER_INCLUDE_DIR . '/test/fakefunctions.php';
-        $this->assertTrue($this->Mail->addAddress('test@françois.ch'));
-    }
-
     public function testErroneousAddress_addAddress_returns_false()
     {
         $this->assertFalse($this->Mail->addAddress('mehome.com'));