Revert "Remove unused test data files"

This reverts commit ef24980e667debd0cb8f1f26218c452bacbbe084.
diff --git a/tests/data_files/passwd.psk b/tests/data_files/passwd.psk
new file mode 100644
index 0000000..17fee37
--- /dev/null
+++ b/tests/data_files/passwd.psk
@@ -0,0 +1 @@
+Client_identity:6162636465666768696a6b6c6d6e6f70