Create utility method to generate file manifests

Refs: #3431

Change-Id: I1a0f06b87689e71349b4fa9346ebc29e785d86cc
diff --git a/tests/testdata/foo/bar.txt b/tests/testdata/foo/bar.txt
new file mode 100644
index 0000000..a8a9406
--- /dev/null
+++ b/tests/testdata/foo/bar.txt
@@ -0,0 +1 @@
+this is a test
\ No newline at end of file