fix(ai): release horn when human driver takes over from AI

tests/unit/CMakeLists.txt

@@ -0,0 +1,31 @@
+# Unit tests of the simulation, built and run without the game data: the test vehicles are JSON
+# definitions in data/ (see vehicle.h), loaded from memory by the game's own vehicle loader. The code
+# under test is the game's core library (eu07_core), the very objects the game links; the rest of the
+# engine it reaches for is replaced with stubs (engine_stubs.cpp). They run as part of the build,
+# from the IDE, or with ctest.
+
+set(UNIT_TESTS_NAME eu07_unit_tests)
+
+# a new test_*.cpp file or data/*.json definition is picked up on its own
+file(GLOB UNIT_TEST_CASES CONFIGURE_DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/test_*.cpp")
+file(GLOB UNIT_TEST_DATA CONFIGURE_DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/data/*.json")
+
+add_executable(${UNIT_TESTS_NAME}
+	main.cpp
+	vehicle.cpp
+	engine_stubs.cpp
+	${UNIT_TEST_CASES})
+
+# the core library brings the game's build settings along
+target_link_libraries(${UNIT_TESTS_NAME} PRIVATE eu07_core)
+target_include_directories(${UNIT_TESTS_NAME} PRIVATE "${DEPS_DIR}/doctest")
+target_compile_definitions(${UNIT_TESTS_NAME} PRIVATE EU07_UNIT_TESTS_DATA="${CMAKE_CURRENT_SOURCE_DIR}/data")
+if (MSVC)
+	target_compile_options(${UNIT_TESTS_NAME} PRIVATE /bigobj)
+endif()
+set_target_properties(${UNIT_TESTS_NAME} PROPERTIES FOLDER "tests")
+
+add_test(NAME ${UNIT_TESTS_NAME} COMMAND ${UNIT_TESTS_NAME})
+
+# for running the tests at the end of building the game, see the main CMakeLists.txt
+set(UNIT_TEST_DATA ${UNIT_TEST_DATA} PARENT_SCOPE)