test: add test for new getDisplayUser() method in OC\User\Manager

Signed-off-by: Kent Delante <kent@delante.me>

Assisted-by: ClaudeCode:claude-sonnet-5

Author: leftybournes

tests/lib/User/ManagerTest.php

@@ -15,6 +15,7 @@
 use OC\User\User;
 use OCP\Config\IUserConfig;
 use OCP\EventDispatcher\IEventDispatcher;
+use OCP\Federation\ICloudId;
 use OCP\ICache;
 use OCP\ICacheFactory;
 use OCP\IConfig;
@@ -762,4 +763,18 @@ public function testGetExistingUser() {
 		$this->assertEquals('nobody', $user->getUID());
 		$this->assertEquals('None', $user->getDisplayName());
 	}
+
+	public function testGetFederatedUser(): void {
+		$userId = 'test@example.com';
+
+		$cloudId = $this->createMock(ICloudId::class);
+		$cloudId->expects($this->exactly(2))
+			->method('getDisplayId')
+			->willReturn($userId);
+
+		$user = $this->manager->getFederatedUser($cloudId);
+
+		$this->assertEquals($userId, $user->getUID());
+		$this->assertEquals($userId, $user->getDisplayName());
+	}
 }