Make the test pass on repeating calls

Signed-off-by: Joas Schilling <coding@schilljs.com>

apps/oauth2/tests/Db/ClientMapperTest.php

@@ -40,6 +40,13 @@ class ClientMapperTest extends TestCase {
 		$this->clientMapper = new ClientMapper(\OC::$server->getDatabaseConnection());
 	}
 
+	protected function tearDown(): void {
+		$query = \OC::$server->getDatabaseConnection()->getQueryBuilder();
+		$query->delete('oauth2_clients')->execute();
+
+		parent::tearDown();
+	}
+
 	public function testGetByIdentifier() {
 		$client = new Client();
 		$client->setClientIdentifier('MyAwesomeClientIdentifier');
@@ -51,7 +58,6 @@ class ClientMapperTest extends TestCase {
 		$this->assertEquals($client, $this->clientMapper->getByIdentifier('MyAwesomeClientIdentifier'));
 	}
 
-	
 	public function testGetByIdentifierNotExisting() {
 		$this->expectException(\OCA\OAuth2\Exceptions\ClientNotFoundException::class);
 
@@ -69,7 +75,6 @@ class ClientMapperTest extends TestCase {
 		$this->assertEquals($client, $this->clientMapper->getByUid($client->getId()));
 	}
 
-	
 	public function testGetByUidNotExisting() {
 		$this->expectException(\OCA\OAuth2\Exceptions\ClientNotFoundException::class);