Fix loading missing files post deployment

agent/build/signature.txt

@@ -1 +1 @@
-52149106D34A73BB8DE3CD83918A1272E980EFE1FADFFC8A80002F96E76429866F7DEB68D99456C71E4D01E85F89D936C6805BD7E40CB772580DCF30BB27A1EB
+AEFC6C5B33B8A0A3AEB075A6C8E2DFEA5D0B1AE302014601999F45C6F5C68A5AA2D50F490F472BC05932163737CEBDFA4EEE066D006415E7BF8C5FD7E3F6FEA9

agent/src/agent.php

@@ -58,6 +58,7 @@
 $ingestTimeout ??= 10;
 /** @var ?string $server */
 $server ??= (string) gethostname();
+$testing = (bool) ($_SERVER['NIGHTWATCH_TESTING'] ?? false);
 
 /*
  * Logging helpers...
@@ -84,7 +85,11 @@
 if ($expectedSignature === false) {
     $error("Unable to read the agent's signature");
 
-    return;
+    if ($testing) {
+        return;
+    } else {
+        exit(1);
+    }
 }
 
 $tokenHash = substr(hash('xxh128', $refreshToken), 0, 7);
@@ -196,3 +201,16 @@
 $checkSignature->start();
 
 $loop->run();
+
+if (! $testing) {
+    // When the agent is invoked from the artisan command, it is possible that
+    // the Laravel application will attempt to load additional PHP files after
+    // the agent has shut down. These additional PHP files are part of their
+    // application not one of the agent's dependencies. If the application is
+    // using a symlink switch deployment strategy, e.g., Laravel Envoyer, it is
+    // possible the additional files are no longer present, which will trigger
+    // a fatal PHP error. Exiting here ensures that the agent always shuts down
+    // cleanly with the tradeoff that the application's terminating hooks will
+    // not run for the `nightwatch:agent` command.
+    exit(0);
+}

agent/tests/TestCase.php

@@ -62,6 +62,9 @@ protected function runAgent(
             }
 
             $process = Process::fromShellCommandline('php '.__DIR__.'/agent-wrapper.php')
+                ->setEnv([
+                    'NIGHTWATCH_TESTING' => '1',
+                ])
                 ->setTimeout($timeout);
 
             $process->mustRun(function (string $type, string $o) use ($until, $process, &$output) {