The internal helper variable '_GOOGLETEST_DISCOVER_TESTS_SCRIPT' can have gone
out-of-scope when 'gtest_discover_tests()' is called, depending on where the
GoogleTest module is actually included. This leads to a silent failure of
dynamic test discovery, since the custom post-build commands actually does
nothing (it basically invokes 'cmake -P ""'). Ctest will then fail to run the
tests, considering them to be 'not built'.
Fix this by determining the path to the GoogleTest module based on
'${CMAKE_ROOT}' instead, which is always available.
A new test case was added to test suite 'RunCMake/GoogleTest' to ensure that
'gtest_discover_tests()' works correctly when invoked in a different variable
scope.
Fixes: #25477
CMake Tests Directory
*********************
This directory contains the CMake test suite.
See also the `CMake Source Code Guide`_.
.. _`CMake Source Code Guide`: ../Help/dev/source.rst
Many tests exist as immediate subdirectories, but some tests
are organized as follows.
* ``CMakeLib/``:
Source code, used for tests, that links to the ``CMakeLib`` library
defined over in ``Source/``.
* ``CMakeOnly/``:
Deprecated. Tests that run CMake to generate a project but not build it.
Superseded by ``Tests/RunCMake/``.
* ``Find*/``:
Tests for specific find modules that can only be run on machines with
the corresponding packages installed. They are enabled in
``CMakeLists.txt`` by undocumented options used on CI builds.
* ``Module/``:
Tests for specific CMake modules.
* ``RunCMake/``:
Tests that run CMake and/or other tools while precisely checking
their return code and stdout/stderr content. Useful for testing
error cases and diagnostic output.
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