enable_testing() activates testing support. add_test(NAME name COMMAND cmd) registers a test that CMake/CTest will run. Tests are commands; their exit code determines pass (0) or fail (non-zero).

Basic setup:

cmake_minimum_required(VERSION 3.20)
project(MyApp)
 
enable_testing()
 
add_executable(test_app test.cpp)
add_test(NAME MyTest COMMAND test_app)

Running tests:

cmake --build . --target test
# or
ctest
ctest -V            # verbose: show output
ctest -R pattern    # run matching tests
ctest -j 4          # run 4 tests in parallel

Multiple tests:

enable_testing()
 
add_executable(test_math test_math.cpp)
add_test(NAME MathTest COMMAND test_math)
 
add_executable(test_string test_string.cpp)
add_test(NAME StringTest COMMAND test_string)

Test with framework (example: Google Test / gtest):

find_package(GTest REQUIRED)
 
add_executable(test_app test.cpp)
target_link_libraries(test_app PRIVATE GTest::gtest GTest::gtest_main)
add_test(NAME GoogleTests COMMAND test_app)

Test properties:

add_test(NAME MyTest COMMAND test_app)
set_tests_properties(MyTest PROPERTIES
  TIMEOUT 10          # timeout after 10 seconds
  DEPENDS OtherTest   # run after OtherTest
  LABELS unit         # label for filtering
)
 
ctest -L unit        # run tests labeled "unit"

Working directory:

add_test(NAME FileTest COMMAND test_app
  WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/test_data)

Conditional tests:

if(BUILD_TESTING)
  enable_testing()
  add_executable(test_app test.cpp)
  add_test(NAME MyTest COMMAND test_app)
endif()

Then build with:

cmake -DBUILD_TESTING=ON ..

Tests typically live in a tests/ or test/ subdirectory:

# CMakeLists.txt
add_subdirectory(tests)
 
# tests/CMakeLists.txt
enable_testing()
add_executable(test_unit unit.cpp)
add_test(NAME UnitTests COMMAND test_unit)

Testing is essential for catching regressions. Enable it early and run tests frequently. CMake integrates with CTest (test runner) and CPack (installer), so test results can be submitted to a dashboard.