diff --git a/tests/shibboleth-idp.bats b/tests/shibboleth-idp.bats
index a2b2640..71ab5f4 100644
--- a/tests/shibboleth-idp.bats
+++ b/tests/shibboleth-idp.bats
@@ -15,4 +15,9 @@ load ../common
 @test "Contains java" {
   run docker run -i bigfleet/shibboleth_idp which java
   [ "$status" -eq 0 ]
+}
+
+@test "Defers configuration via ONBUILD" {
+ run grep ONBUILD Dockerfile
+ [ "$status" -eq 1 ]
 }
\ No newline at end of file