CMake/Tests/RunCMake

This directory contains tests that run CMake to configure a project
but do not actually build anything. To add a test:

1. Add a subdirectory named for the test, say ``/``.

2. In ``./CMakeLists.txt`` call ``add_RunCMake_test`` and pass the
test directory name ````.

3. Create script ``/RunCMakeTest.cmake`` in the directory containing::

include(RunCMake)
run_cmake(SubTest1)
...
run_cmake(SubTestN)

where ``SubTest1`` through ``SubTestN`` are sub-test names each
corresponding to an independent CMake run and project configuration.

One may also add calls of the form::

run_cmake_command(SubTestI ${CMAKE_COMMAND} ...)

to fully customize the test case command-line.

Alternatively, if the test is to cover running ``ctest -S`` then use::

include(RunCTest)
run_ctest(SubTest1)
...
run_ctest(SubTestN)

and create ``test.cmake.in``, ``CTestConfig.cmake.in``, and
``CMakeLists.txt.in`` files to be configured for each case.

4. Create file ``/CMakeLists.txt`` in the directory containing::

cmake_minimum_required(...)
project(${RunCMake_TEST} NONE) # or languages needed
include(${RunCMake_TEST}.cmake)

where ``${RunCMake_TEST}`` is literal. A value for ``RunCMake_TEST``
will be passed to CMake by the ``run_cmake`` macro when running each
sub-test.

5. Create a ``/.cmake`` file for each sub-test named
above containing the actual test code. Optionally create files
containing expected test results:

``-result.txt``
Regex matching expected process result, if not ``0``
``-stdout.txt``
Regex matching expected stdout content
``-stderr.txt``
Regex matching expected stderr content, if not ``^$``
``-check.cmake``
Custom result check.

Note that trailing newlines will be stripped from actual and expected
test output before matching against the stdout and stderr expressions.
The code in ``-check.cmake`` may use variables

``RunCMake_TEST_SOURCE_DIR``
Top of test source tree
``RunCMake_TEST_BINARY_DIR``
Top of test binary tree

and an failure must store a message in ``RunCMake_TEST_FAILED``.

To speed up local testing, you can choose to run only a subset of
``run_cmake()`` tests in a ``RunCMakeTest.cmake`` script by using the
``RunCMake_TEST_FILTER`` environment variable. If this variable is set,
it is treated as a regular expression, and any tests whose names don't
match the regular expression are not run. For example::

$ RunCMake_TEST_FILTER="^example" ctest -R '^RunCMake\.Example$'

This will only run subtests in ``RunCMake.Example`` that start with
``example``.