Today, let’s talk about testing with CMake.

But actually, we are still talking about testing in C++.

CMake provides us with comprehensive testing support, such as its dedicated module, CTest.

Native CMake Testing Support

Native testing support in CMake is quite simple, involving only two functions:

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enable_testing()
add_test(NAME <name> COMMAND <command> [<arg>...]
         [CONFIGURATIONS <config>...]
         [WORKING_DIRECTORY <dir>]
         [COMMAND_EXPAND_LISTS])

Simply put, you first need to implement an executable program that can take input parameters using add_executable, without worrying about the location of this executable as CMake will handle it automatically.

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enable_testing()

add_executable(test_example test.cpp)
target_link_libraries(test_example example_lib)

add_test(NAME test_example1 COMMAND test_example --arg1=a --arg2=b)
add_test(NAME test_example2 COMMAND test_example --arg1=c --arg2=d)

After registering your test cases with add_test, the setup is complete. You can then run the test cases using one of the following three methods after compilation:

  • make test
  • cmake --build . --target test
  • ctest

Of course, you can also use CTest in conjunction with CDash, which is a place that can log test results. You can explore more at https://my.cdash.org/index.php. Generally, there is a need for this kind of capability as projects grow larger.

GoogleTest

Besides the above ctest, we also have the powerful GoogleTest, which is currently the most widely used C++ testing framework. Unlike the need to implement your own testing framework logic and parse parameters, GoogleTest provides a testing framework as well as Mock.

CMake also supports GoogleTest:

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gtest_add_tests(TARGET target
                [SOURCES src1...]
                [EXTRA_ARGS arg1...]
                [WORKING_DIRECTORY dir]
                [TEST_PREFIX prefix]
                [TEST_SUFFIX suffix]
                [SKIP_DEPENDENCY]
                [TEST_LIST outVar]
)

This is meant to replace add_test. By scanning the source code, it can identify all test cases, avoiding the need to rewrite them on both sides. However, it has an issue: once the test cases are changed, it requires re-running cmake to recognize the updated test cases.

Thus, since CMake 3.10, a new method has been provided:

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gtest_discover_tests(target
                     [EXTRA_ARGS arg1...]
                     [WORKING_DIRECTORY dir]
                     [TEST_PREFIX prefix]
                     [TEST_SUFFIX suffix]
                     [NO_PRETTY_TYPES] [NO_PRETTY_VALUES]
                     [PROPERTIES name1 value1...]
                     [TEST_LIST var]
                     [DISCOVERY_TIMEOUT seconds]
)

Compared to gtest_add_tests, gtest_discover_tests registers tests by fetching them from the compiled executable, making it more robust. In case of test case changes, it does not require re-running cmake (the principle is not magical, just run the compiled program with --gtest_list_tests to see).

Using it is straightforward, assuming GoogleTest dependencies are present (if not, review the content from the first two articles). Introduce the dependency with find_package.

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enable_testing()
include(GoogleTest)
find_package(GTest 1.10.0)

add_executable(test test.cpp)
target_link_libraries(test GTest::gtest GTest::gtest_main GTest::gmock
                        GTest::gmock_main)
gtest_discover_tests(test)

Regarding GoogleTest itself, it’s a matter of reading the documentation to write test cases (those interested can leave a comment, and I might write a separate article). Also, as I’ve mentioned in Testing in Golang, the principles for writing unit tests are the same here. Combined with GoogleTest’s Mock, we can make unit testing very straightforward.

Ref

  1. Testing With CTest

First published on Github issues: https://github.com/xizhibei/blog/issues/136, feel free to Star and Watch

This article is licensed BY-NC-SA
Author: 习之北 (@xizhibei)
Original link: https://blog.xizhibei.me/en/2020/04/05/cmake-4-test-with-google-test/