diff --git a/Dockerfile b/Dockerfile
index 602c64a..0e3bc2d 100644
--- a/Dockerfile
+++ b/Dockerfile
@@ -19,6 +19,8 @@ RUN chown -R php:php /usr/bin/app
 COPY . /usr/bin/app
 WORKDIR /usr/bin/app
 
+ENV GITHUB_WORKSPACE=/usr/bin/app
+
 RUN composer install
 
 VOLUME ["/usr/bin/app"]
diff --git a/README.md b/README.md
index b61c4d5..dcc601c 100644
--- a/README.md
+++ b/README.md
@@ -55,15 +55,15 @@ docker build . --build-arg=PHP_VERSION=8.3 -t=composer-package-action
 
 initialization
 ```shell
-docker run --rm -e GITHUB_WORKSPACE=/usr/bin/app -v .:/usr/bin/app composer-package-action composer install
+docker run --rm -v .:/usr/bin/app composer-package-action composer install
 ```
 
 running
 ```shell
-docker run --rm -e GITHUB_WORKSPACE=/usr/bin/app -v .:/usr/bin/app composer-package-action php app.php
+docker run --rm -v .:/usr/bin/app composer-package-action php app.php
 ```
 
 testing
 ```shell
-docker run --rm -e GITHUB_WORKSPACE=/usr/bin/app -v .:/usr/bin/app composer-package-action composer tests
+docker run --rm -v .:/usr/bin/app composer-package-action composer tests
 ```
diff --git a/tests/ActionTest.php b/tests/ActionTest.php
index d6ff8d0..5ab3098 100644
--- a/tests/ActionTest.php
+++ b/tests/ActionTest.php
@@ -11,17 +11,11 @@
 #[CoversClass(Action::class)]
 final class ActionTest extends TestCase
 {
-    /**
-     * @var string
-     */
-    private const string DEFAULT_ENV_GITHUB_WORKSPACE = '/usr/bin/app';
-
     private ?Action $action;
 
     #[\Override]
     protected function setUp(): void
     {
-        putenv('GITHUB_WORKSPACE=' . self::DEFAULT_ENV_GITHUB_WORKSPACE);
         putenv('directory=.build');
 
         $this->action = new Action();
@@ -32,7 +26,6 @@ protected function setUp(): void
     #[\Override]
     protected function tearDown(): void
     {
-        putenv('GITHUB_WORKSPACE=');
         putenv('directory=');
 
         $this->removeBuildDirectory();
@@ -71,7 +64,7 @@ private function removeDirectory(string $dir): void
     {
         $dir = realpath($dir);
 
-        if (is_dir($dir)) {
+        if (is_dir($dir) && is_readable($dir) && is_writable($dir)) {
 
             $iterator = new \RecursiveIteratorIterator(
                 new \RecursiveDirectoryIterator($dir),