Mark test helper functions so that test output is much more useful when failures occur in the helpers.
Mark test helper functions so that test output is much more useful when failures occur in the helpers.

PiperOrigin-RevId: 281597427
Change-Id: I82c583661fd11a682ce6746cacfb9aeeea89f1eb

google/mako,google/mako,google/mako,google/mako