Google C++ Testing Framework Views

Mian Qin · May 5, 2020

C++

I have been noticing that lots of huge C/C++ projects use Google testing framework (i.e. GTest). However, in the past I thought this is not worth integrating third-party testing framework in my medium/small projects. I am used to writing my own test case for unit tests which is simple and flexible to change according to my needs and more importantly doesn’t need any dependant packages. Recently, I found most platforms already has Gtest installed and integrating Gtest to my own project can actually accelerate unit test process with a lot of advanced features (like repeat test and break on failure) provided by Gtest. This blog summarizes the basic elements of Gtest, usage and provide some useful resources.

Overview

When using Gtest, you start by writing assertions, which are statements that check whether a condition is true. An assertion’s result can be success, nonfatal failure, or fatal failure. If a fatal failure occurs, it aborts the current function; otherwise the program continues normally. Tests use assertions to verify the tested code’s behavior. If a test crashes or has a failed assertion, then it fails; otherwise it succeeds.

Semantic

Test Macro

GTest provide two macros to wrapper the unit test, i.e. TEST and TEST_F.

  • TEST, the first argument is the name of the test suite, and the second argument is the test’s name within the test suite. Both names must be valid C++ identifiers, and they should not contain any underscores (_).

  • TEST_F (F stands for fixtures), like TEST(), the first argument is the test suite name, but for TEST_F() this must be the name of the test fixture class. Noted TEST_F is design for more complex unit testing. You can test with test class derived from testing::Test. Below are detailed steps.

    1. Derive a class from ::testing::Test . Start its body with protected:, as we’ll want to access fixture members from sub-classes.
    2. Inside the class, declare any objects you plan to use.
    3. If necessary, write a default constructor or SetUp() function to prepare the objects for each test. A common mistake is to spell SetUp() as Setup() with a small u - Use override in C++11 to make sure you spelled it correctly.
    4. If necessary, write a destructor or TearDown() function to release any resources you allocated in SetUp().
    5. If needed, define subroutines for your tests to share.

Example code can be seen in the gtest primer.

Run tests

After register your test cases through TEST and TEST_F Marcos. You can invoke you tests through a main function and GTest will automatically pick up the test codes like below.

int main(int argc, char **argv) {
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}

Build

After installing the GTest in your system, (either through apt/yum or compiled through source), you can link GTest through

-lgtest -lgtest-main -pthread

Also, you can build through more modern CMake. See here.

Reference

https://developer.ibm.com/articles/au-googletestingframework/

https://github.com/google/googletest/blob/master/googletest/docs/primer.md

https://github.com/google/googletest

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