diff --git a/_test_data/sandbox/clean/grandchild.txt b/_test_data/sandbox/clean/grandchild.txt
new file mode 100644
index 0000000..db3cd4b
--- /dev/null
+++ b/_test_data/sandbox/clean/grandchild.txt
@@ -0,0 +1,3 @@
+clean stack: grandchild branch
+purpose: grandchild PR on top of sandbox-clean-child
+marker: c4706ab