Diagnostic Updater does not find Rostest

[kdhansen]

When installing, I ran into this:

Starting  >>> diagnostic_updater
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Errors     << diagnostic_updater:cmake /Users/kdh/ros-install-osx/lunar_desktop_full_ws/logs/diagnostic_updater/build.cmake.001.log
CMake Error at /Users/kdh/ros-install-osx/lunar_desktop_full_ws/src/diagnostics/diagnostic_updater/CMakeLists.txt:18 (find_package):
  By not providing "Findrostest.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "rostest", but
  CMake did not find one.

  Could not find a package configuration file provided by "rostest" with any
  of the following names:

    rostestConfig.cmake
    rostest-config.cmake

  Add the installation prefix of "rostest" to CMAKE_PREFIX_PATH or set
  "rostest_DIR" to a directory containing one of the above files.  If
  "rostest" provides a separate development package or SDK, be sure it has
  been installed.

I can see that it does not find the cmake config to find rostest referenced in line 17 of the CMakeList in diagnostic_updater, but I am not an CMake expert. So, I do not know how to tell CMake how to find it.