Step by step, this is how to write CMakeLists.txt to accomplish our task:

1. In this recipe, we will not require any language support from CMake, but we will need to locate a working Python interpreter:

cmake_minimum_required(VERSION 3.5 FATAL_ERROR)

project(recipe-06 LANGUAGES NONE)

find_package(PythonInterp REQUIRED)

2. We then define the test and tell CMake that we expect it to fail:

enable_testing()

add_test(example ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/test.py)

set_tests_properties(example PROPERTIES WILL_FAIL true)

3. Finally, we verify that it is reported as a successful test, as follows:

$ mkdir -p build
$ cd build
$ cmake ..
$ cmake --build .
$ ctest

Test project /home/user/cmake-recipes/chapter-04/recipe-06/example/build
    Start 1: example
1/1 Test #1: example .......................... Passed 0.00 sec

100% tests passed, 0 tests failed out of 1

Total Test time (real) = 0.01 sec