diff --git a/commands/web/drupal b/commands/web/drupal
index de9bbe8..6f88c66 100755
--- a/commands/web/drupal
+++ b/commands/web/drupal
@@ -25,6 +25,7 @@ use DrupalCoreDev\Command\LintPhpCsCommand;
 use DrupalCoreDev\Command\LintPhpStanCommand;
 use DrupalCoreDev\Command\ModuleInstallCommand;
 use DrupalCoreDev\Command\TestBrowserCommand;
+use DrupalCoreDev\Command\TestExtensionsCommand;
 use DrupalCoreDev\Command\TestCommand;
 use DrupalCoreDev\Command\UninstallCommand;
 use Symfony\Component\Console\Application;
@@ -46,6 +47,7 @@ $application->add(new CacheCommand($loader));
 $application->add(new AdminLoginCommand($loader));
 $application->add(new GenerateTheme());
 $application->add(new TestCommand());
+$application->add(new TestExtensionsCommand());
 $application->add(new TestBrowserCommand());
 $application->add(new LintPhpCsCommand());
 $application->add(new LintPhpStanCommand());
diff --git a/core-dev/src/Command/ModuleInstallCommand.php b/core-dev/src/Command/ModuleInstallCommand.php
index d6f8de5..b6dc17e 100644
--- a/core-dev/src/Command/ModuleInstallCommand.php
+++ b/core-dev/src/Command/ModuleInstallCommand.php
@@ -29,6 +29,8 @@ protected function execute(InputInterface $input, OutputInterface $output): int
           $module_installer = \Drupal::service('module_installer');
           assert($module_installer instanceof ModuleInstallerInterface);
           $module_installer->install($modules);
+          $kernel = \Drupal::service('kernel');
+          $kernel->rebuildContainer();
       }
       return 0;
     }
diff --git a/core-dev/src/Command/TestExtensionsCommand.php b/core-dev/src/Command/TestExtensionsCommand.php
new file mode 100644
index 0000000..bb7484a
--- /dev/null
+++ b/core-dev/src/Command/TestExtensionsCommand.php
@@ -0,0 +1,65 @@
+<?php
+#ddev-generated
+
+namespace DrupalCoreDev\Command;
+
+use Symfony\Component\Console\Command\Command;
+use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Input\InputOption;
+use Symfony\Component\Console\Output\OutputInterface;
+use Symfony\Component\Console\Style\SymfonyStyle;
+use Symfony\Component\Process\Process;
+
+class TestExtensionsCommand extends Command {
+    /**
+     * {@inheritdoc}
+     */
+    protected function configure(): void {
+        $this->setName('test:extensions-enable')
+          ->setDescription('Allow test modules and themes to be installed');
+    }
+
+    /**
+     * {@inheritdoc}
+     */
+    protected function execute(InputInterface $input, OutputInterface $output): int {
+        $io = new SymfonyStyle($input, $output);
+        $setting = "\$settings['extension_discovery_scan_tests'] = TRUE;\n";
+        $file = __DIR__ . '/../../../../sites/default/settings.php';
+        $data = file_get_contents($file);
+        if (str_contains($data, $setting)) {
+            return 0;
+        }
+
+        $mode = null;
+        if (!is_writable($file)) {
+            try {
+                $stat = stat($file);
+                chmod($file, 0744);
+            }
+            catch (\Error $e) {
+                $io->getErrorStyle()->error("Could not set $file to writeable");
+                return 1;
+            }
+            $mode = $stat['mode'] & 000777;
+        }
+
+
+        file_put_contents($file, $setting, FILE_APPEND);
+        $output->writeln('extension_discovery_scan_tests enabled in settings.php');
+
+        if (!is_null($mode)) {
+            // Reverse the array of unhardened paths because we want to change the
+            // child item before the parent item.
+            try {
+                chmod($file, $mode);
+            }
+            catch (\Error $e) {
+                $io->getErrorStyle()->error("Unable to reharden permissions for $file");
+                return 1;
+            }
+        }
+
+        return 0;
+    }
+}
diff --git a/install.yaml b/install.yaml
index c70c41c..217a555 100644
--- a/install.yaml
+++ b/install.yaml
@@ -17,6 +17,7 @@ project_files:
   - core-dev/src/Command/CacheCommand.php
   - core-dev/src/Command/TestCommand.php
   - core-dev/src/Command/TestBrowserCommand.php
+  - core-dev/src/Command/TestExtensionsCommand.php
   - core-dev/src/Command/UninstallCommand.php
   - core-dev/src/Command/LintPhpCsCommand.php
   - core-dev/src/Command/LintPhpStanCommand.php