diff --git a/tests/Composer/Test/Command/ConfigCommandTest.php b/tests/Composer/Test/Command/ConfigCommandTest.php
index 10dd170f2..68653c622 100644
--- a/tests/Composer/Test/Command/ConfigCommandTest.php
+++ b/tests/Composer/Test/Command/ConfigCommandTest.php
@@ -13,6 +13,7 @@
 namespace Composer\Test\Command;
 
 use Composer\Test\TestCase;
+use RuntimeException;
 
 class ConfigCommandTest extends TestCase
 {
@@ -139,4 +140,13 @@ class ConfigCommandTest extends TestCase
             '{"foo":{"type":"vcs","url":"https://example.org"}}',
         ];
     }
+
+    public function testConfigThrowsForInvalidArgCombination(): void
+    {
+        $this->expectException(RuntimeException::class);
+        $this->expectExceptionMessage('--file and --global can not be combined');
+
+        $appTester = $this->getApplicationTester();
+        $appTester->run(['command' => 'config', '--file' => 'alt.composer.json', '--global' => true]);
+    }
 }