diff --git a/testdata/invalid__err.ct b/testdata/invalid__err.ct
new file mode 100644
index 0000000..1bd0417
--- /dev/null
+++ b/testdata/invalid__err.ct
@@ -0,0 +1,3 @@
+$ pda invalidcmd --> FAIL
+Error: unknown command "invalidcmd" for "pda"
+Run 'pda --help' for usage.