diff --git a/tests/Sabre/DAV/AbstractServerTestCase.php b/tests/Sabre/DAV/AbstractServerTestCase.php
index 053a229dbc..dcc2e908bf 100644
--- a/tests/Sabre/DAV/AbstractServerTestCase.php
+++ b/tests/Sabre/DAV/AbstractServerTestCase.php
@@ -25,7 +25,7 @@ abstract class AbstractServerTestCase extends TestCase
     public function setup(): void
     {
         $this->response = new ResponseMock();
-        $this->server = new Server($this->getRootNode());
+        $this->server = new ServerMock($this->getRootNode());
         $this->server->sapi = new HTTP\SapiMock();
         $this->server->httpResponse = $this->response;
         $this->server->debugExceptions = true;
diff --git a/tests/Sabre/DAV/Locks/PluginTest.php b/tests/Sabre/DAV/Locks/PluginTest.php
index 465bbc1609..7971c3f674 100644
--- a/tests/Sabre/DAV/Locks/PluginTest.php
+++ b/tests/Sabre/DAV/Locks/PluginTest.php
@@ -321,7 +321,7 @@ public function testLockPutNoToken()
         $this->server->exec();
 
         self::assertEquals('application/xml; charset=utf-8', $this->response->getHeader('Content-Type'));
-        self::assertTrue(1 === preg_match('/^<opaquelocktoken:(.*)>$/', $this->response->getHeader('Lock-Token')), 'We did not get a valid Locktoken back ('.$this->response->getHeader('Lock-Token').')');
+        self::assertFalse($this->response->hasHeader('Lock-Token'), 'Unexpected Lock-Token in response');
 
         self::assertEquals(423, $this->response->status);
     }
@@ -451,7 +451,7 @@ public function testLockPutBadToken()
         $this->server->exec();
 
         self::assertEquals('application/xml; charset=utf-8', $this->response->getHeader('Content-Type'));
-        self::assertTrue(1 === preg_match('/^<opaquelocktoken:(.*)>$/', $this->response->getHeader('Lock-Token')), 'We did not get a valid Locktoken back ('.$this->response->getHeader('Lock-Token').')');
+        self::assertFalse($this->response->hasHeader('Lock-Token'), 'We did get unexpected Lock-Token header back in PUT response');
 
         // self::assertEquals('412 Precondition failed',$this->response->status);
         self::assertEquals(423, $this->response->status);
@@ -518,7 +518,7 @@ public function testLockDeleteSucceed()
         $this->server->exec();
 
         self::assertEquals(204, $this->response->status);
-        self::assertEquals('application/xml; charset=utf-8', $this->response->getHeader('Content-Type'));
+        self::assertNull($this->response->body);
     }
 
     /**
@@ -591,7 +591,7 @@ public function testLockCopyLockSource()
         $this->server->exec();
 
         self::assertEquals(201, $this->response->status, 'Copy must succeed if only the source is locked, but not the destination');
-        self::assertEquals('application/xml; charset=utf-8', $this->response->getHeader('Content-Type'));
+        self::assertNull($this->response->body);
     }
 
     /**
@@ -759,7 +759,7 @@ public function testLockMoveLockParent()
         $this->server->exec();
 
         self::assertEquals(201, $this->response->status, 'We locked the parent of both the source and destination, but the move didn\'t succeed.');
-        self::assertEquals('application/xml; charset=utf-8', $this->response->getHeader('Content-Type'));
+        self::assertNull($this->response->body);
     }
 
     /**
@@ -792,8 +792,8 @@ public function testLockPutGoodToken()
         $this->server->httpRequest = $request;
         $this->server->exec();
 
-        self::assertEquals('application/xml; charset=utf-8', $this->response->getHeader('Content-Type'));
-        self::assertTrue(1 === preg_match('/^<opaquelocktoken:(.*)>$/', $this->response->getHeader('Lock-Token')), 'We did not get a valid Locktoken back ('.$this->response->getHeader('Lock-Token').')');
+        self::assertNull($this->response->body);
+        self::assertFalse($this->response->hasHeader('Lock-Token'), 'Unexpected Lock-Token header');
 
         self::assertEquals(204, $this->response->status);
     }
@@ -830,8 +830,8 @@ public function testLockPutUnrelatedToken()
         $this->server->httpRequest = $request;
         $this->server->exec();
 
-        self::assertEquals('application/xml; charset=utf-8', $this->response->getHeader('Content-Type'));
-        self::assertTrue(1 === preg_match('/^<opaquelocktoken:(.*)>$/', $this->response->getHeader('Lock-Token')), 'We did not get a valid Locktoken back ('.$this->response->getHeader('Lock-Token').')');
+        self::assertNull($this->response->body);
+        self::assertFalse($this->response->hasHeader('Lock-Token'), 'Unexpected Lock-Token header');
 
         self::assertEquals(204, $this->response->status);
     }
diff --git a/tests/Sabre/DAV/ServerMock.php b/tests/Sabre/DAV/ServerMock.php
new file mode 100644
index 0000000000..bac419a60d
--- /dev/null
+++ b/tests/Sabre/DAV/ServerMock.php
@@ -0,0 +1,25 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sabre\DAV;
+
+/**
+ * DAV Server Mock object.
+ *
+ * @copyright Copyright (C) fruux GmbH (https://fruux.com/)
+ * @author Evert Pot (http://evertpot.com/)
+ * @license http://sabre.io/license/ Modified BSD License
+ */
+class ServerMock extends Server
+{
+    /**
+     * Starts the DAV Server making sure the mocked response state is reset.
+     */
+    public function start()
+    {
+        $this->httpResponse->reset();
+
+        parent::start();
+    }
+}
diff --git a/tests/Sabre/HTTP/ResponseMock.php b/tests/Sabre/HTTP/ResponseMock.php
index 0d968e178f..318ee6afa3 100644
--- a/tests/Sabre/HTTP/ResponseMock.php
+++ b/tests/Sabre/HTTP/ResponseMock.php
@@ -20,4 +20,15 @@ class ResponseMock extends Response
      */
     public $body;
     public int $status;
+
+    /**
+     * Reset the response state. Needed if making more than one request in a single test.
+     */
+    public function reset()
+    {
+        $this->headers = [];
+        $this->body = null;
+        $this->status = 500;
+        $this->statusText = '';
+    }
 }