Test-Driven Development in C++ with Google Test

Google Test (gtest) is a popular testing framework for C++. It provides the ability to create automated tests, which are essential for ensuring your code behaves as expected. In this post, we'll cover how to set up Google Test and use it for Test-Driven Development (TDD) in C++.

What is Google Test?

Google Test is a powerful, open-source testing framework developed by Google. It's designed to work well with the C++ programming language and provides features that simplify the process of writing tests.

Setting Up Google Test

Before we can use Google Test, we need to install it. Here's how you can do it on a Unix-like system:

sudo apt-get install libgtest-dev
cd /usr/src/gtest
sudo cmake CMakeLists.txt
sudo make
sudo cp *.a /usr/lib

On Windows, you can download the source code from the Google Test GitHub repository and build it using CMake.

Writing Your First Test

Let's write a simple test for a function that adds two numbers. First, we'll write the function:

int add(int a, int b) {
    return a + b;
}

Now, we can write a test for this function:

#include <gtest/gtest.h>

TEST(AddTest, HandlesPositiveInput) {
    EXPECT_EQ(6, add(2, 4));
}

In this code, TEST is a macro that defines a test function. The first argument is the test case name, and the second argument is the individual test name. EXPECT_EQ is an assertion that expects the two arguments to be equal.

Test-Driven Development with Google Test

Test-Driven Development (TDD) is a software development approach where you write a test before you write the code to pass that test. Here's a simple example:

1. Write a test for a function that isn't implemented yet:

TEST(SquareTest, HandlesPositiveInput) {
    EXPECT_EQ(4, square(2));
}

2. Run the test. It should fail because the square function isn't implemented yet.

3. Implement the square function:

int square(int a) {
    return a * a;
}

4. Run the test again. It should pass now. This is a simple example, but it illustrates the TDD process: write a test, write code to pass the test, and then refactor as necessary.

Conclusion

Google Test is a powerful tool for writing tests in C++. Combined with the Test-Driven Development approach, it can help you write more reliable, bug-free code. Stay tuned for more posts on advanced testing techniques and best practices!