diff --git a/TESTING_dockercompose.md b/TESTING_dockercompose.md
index 450f641..50968a0 100644
--- a/TESTING_dockercompose.md
+++ b/TESTING_dockercompose.md
@@ -69,6 +69,10 @@ docker-compose exec -T cli bash -c "yarn --version"
 # Should have a running Drupal 9 site served by nginx on port 8080
 docker-compose exec -T cli bash -c "curl -kL http://nginx:8080" | grep "Drush Site-Install"
 
+# Internal files are not served by Nginx.
+docker-compose exec -T cli bash -c "curl -sI http://nginx:8080/composer.json" | grep "404 Not Found"
+docker-compose exec -T cli bash -c "curl -sI http://nginx:8080/core/composer.json" | grep "404 Not Found"
+
 # Should be able to db-export and db-import the database
 docker-compose exec -T cli bash -c "drush sql-dump --result-file /app/test.sql"
 docker-compose exec -T cli bash -c "drush sql-drop -y"
diff --git a/TESTING_lando.md b/TESTING_lando.md
index 2998266..be1ed7e 100644
--- a/TESTING_lando.md
+++ b/TESTING_lando.md
@@ -73,6 +73,10 @@ lando lagoon --version | grep lagoon
 # Should have a running Drupal 9 site served by nginx on port 8080
 lando ssh -s cli -c "curl -kL http://nginx:8080" | grep "Welcome to Drush Site-Install"
 
+# Internal files are not served by Nginx.
+lando ssh -s cli -c "curl -sI http://nginx:8080/composer.json" | grep "404 Not Found"
+lando ssh -s cli -c "curl -sI http://nginx:8080/core/composer.json" | grep "404 Not Found"
+
 # Should be able to db-export and db-import the database
 lando db-export test.sql
 lando db-import test.sql.gz