diff --git a/tests/AcquiaCliApplicationTest.php b/tests/AcquiaCliApplicationTest.php
index fb75547..5d93ac4 100644
--- a/tests/AcquiaCliApplicationTest.php
+++ b/tests/AcquiaCliApplicationTest.php
@@ -8,9 +8,12 @@
 use AcquiaCli\Cli\AcquiaCli;
 use Symfony\Component\Console\Output\BufferedOutput;
 use Symfony\Component\Stopwatch\Stopwatch;
+use Symfony\Component\Console\Command\LockableTrait;
 
 class AcquiaCliApplicationTest extends AcquiaCliTestCase
 {
+    use LockableTrait;
+
     private $root;
 
     public function setUp()
@@ -49,6 +52,18 @@ public function testVersion()
         $this->assertContains('AcquiaCli 2', $actualValue);
     }
 
+    public function testLock()
+    {
+        // Obtain an identical lock and then attempt to run acquiacli.
+        $this->lock('acquia-cli-command');
+        $command = ['--version'];
+        $actualValue = $this->execute($command);
+        $this->assertContains('The command is already running in another process.', $actualValue);
+
+        // Unlock to ensure tests are able to continue.
+        $this->release();
+    }
+
     public function testClientOptions()
     {
         $command = ['application:list', '--sort=label', '--filter=label=@*sample*', '--limit=2'];