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cplusplus/geminitutorial/tutorial1/tutorial-part1-2.md
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cplusplus/geminitutorial/tutorial1/tutorial-part1-2.md
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# Tutorial 1.2: Introduction to Unit Testing
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**Objective:** To introduce unit testing to the C++ project from Tutorial 1.1. This tutorial will cover adding a testing framework (`googletest`), creating a simple class, writing tests for that class, and integrating the tests into the CMake build system for easy execution within VSCode.
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---
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## 1. Prerequisites
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* A completed and working project from "Tutorial 1.1: Your First Modern C++ Project".
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* `vcpkg` installed and configured as per Tutorial 1.1.
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---
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## 2. Installing the Testing Framework
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We will use `googletest`, a popular and powerful testing framework for C++.
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Just like with `spdlog`, we use `vcpkg` to install it.
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```bash
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# Use the vcpkg executable to install the library
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# Replace /path/to/vcpkg with your actual vcpkg path
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/home/YOUR_USERNAME/dev/tools/vcpkg/vcpkg install gtest
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```
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*Note: The package name is `gtest` for `googletest`.*
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---
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## 3. Refactoring the Project Structure
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To keep our project organized, we'll separate our main application code from the test code. The new structure inside `tutorial-1` will look like this:
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```
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tutorial-1/
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├── CMakeLists.txt
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├── src/
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│ ├── calculator.h
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│ ├── calculator.cpp
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│ └── main.cpp
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└── test/
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└── test_calculator.cpp
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```
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The previous steps in this session have already created this structure for you.
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---
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## 4. Creating a Class to Test
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We need some logic to test. We've created a simple `Calculator` class.
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**File:** `tutorial-1/src/calculator.h`
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```cpp
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#ifndef CALCULATOR_H
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#define CALCULATOR_H
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class Calculator {
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public:
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int add(int a, int b);
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};
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#endif // CALCULATOR_H
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```
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**File:** `tutorial-1/src/calculator.cpp`
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```cpp
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#include "calculator.h"
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int Calculator::add(int a, int b) {
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return a + b;
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}
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```
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We also updated `main.cpp` to use this new class.
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**File:** `tutorial-1/src/main.cpp` (Updated)
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```cpp
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#include <iostream>
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#include "spdlog/spdlog.h"
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#include "calculator.h"
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int main() {
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spdlog::info("Hello, Modern C++! Initializing trading strategy...");
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Calculator calc;
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int result = calc.add(40, 2);
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spdlog::info("The result of 40 + 2 is: {}", result);
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std::cout << "Check your terminal for spdlog output!" << std::endl;
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return 0;
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}
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```
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---
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## 5. Writing the Unit Tests
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Now, we'll write our first test in the `test` directory.
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**File:** `tutorial-1/test/test_calculator.cpp`
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```cpp
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#include <gtest/gtest.h>
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#include "../src/calculator.h" // Include the header for the class we are testing
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// Test fixture for Calculator class
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class CalculatorTest : public ::testing::Test {
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protected:
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Calculator calc;
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};
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// Test case for the add method
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TEST_F(CalculatorTest, Add) {
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EXPECT_EQ(calc.add(2, 2), 4);
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EXPECT_EQ(calc.add(-1, 1), 0);
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EXPECT_EQ(calc.add(-5, -5), -10);
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}
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// Another test case for the add method for good measure
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TEST_F(CalculatorTest, AddWithZero) {
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EXPECT_EQ(calc.add(0, 5), 5);
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EXPECT_EQ(calc.add(5, 0), 5);
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EXPECT_EQ(calc.add(0, 0), 0);
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}
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```
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---
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## 6. Updating the Build System (CMake)
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This is the most critical part. We have updated our `CMakeLists.txt` to build both our main application and our tests as separate executables.
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**File:** `tutorial-1/CMakeLists.txt` (Updated)
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```cmake
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cmake_minimum_required(VERSION 3.15)
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project(Tutorial1 LANGUAGES CXX)
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set(CMAKE_CXX_STANDARD 17)
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set(CMAKE_CXX_STANDARD_REQUIRED ON)
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# Find dependencies
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find_package(spdlog CONFIG REQUIRED)
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find_package(GTest CONFIG REQUIRED)
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# Create a library for our application code
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# This allows us to share the code between the main app and the tests
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add_library(MyLib src/calculator.cpp src/calculator.h)
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target_include_directories(MyLib PUBLIC src)
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# Define our main executable
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add_executable(App src/main.cpp)
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# Link our App against spdlog and our library
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target_link_libraries(App PRIVATE spdlog::spdlog MyLib)
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# Enable testing with CTest (CMake's testing framework)
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enable_testing()
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# Define the test executable
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add_executable(RunTests test/test_calculator.cpp)
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# Link our test executable against GTest and our library
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target_link_libraries(RunTests PRIVATE GTest::GTest GTest::Main MyLib)
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# Add the test to CTest
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include(GoogleTest)
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gtest_add_tests(TARGET RunTests)
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```
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---
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## 7. Building and Running Tests in VSCode
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1. **Install `gtest`:** Make sure you have installed `gtest` using `vcpkg` as described in step 2.
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2. **Configure CMake:** Run `CMake: Configure` from the command palette (Ctrl+Shift+P). It should detect the changes and find `gtest`.
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3. **Build:** Click the **Build** button in the status bar. This will now build `App` and `RunTests`.
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4. **Run Tests:** The "CMake Tools" extension provides a "Test Explorer" view in VSCode.
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* Open the Test Explorer from the side bar (the icon looks like a beaker).
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* You should see your test suite (`CalculatorTest`) and the individual tests.
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* Click the "play" button at the top of the Test Explorer to run all tests.
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* You can also run individual tests. The results will be shown directly in the UI.
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---
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**Congratulations!** You have now added unit testing to your project. This is a crucial skill for writing robust and maintainable C++ applications. You've learned how to:
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* Add a testing library (`googletest`) with `vcpkg`.
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* Structure your project to separate app code from test code.
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* Create a shared library and multiple executables with CMake.
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* Write and run unit tests using the VSCode Test Explorer.
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## Feedback and Questions
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1. The line ```target_link_libraries(RunTests PRIVATE GTest::GTest GTest::Main MyLib)``` caused cmake compilation error, I changed to
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```target_link_libraries(RunTests PRIVATE GTest::gtest_main MyLib)```
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I looked up documentation for this.
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2. Are there alternative ways to install dependencies other the through vcpkg? For example would FetchContent work (https://cmake.org/cmake/help/latest/module/FetchContent.html)?
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3.Interestingly, in vscode, the line ```#include <gtest/gtest.h>``` i was curious where the files as located - as i had not specified where it is other the download gtest in a separate process via vcpkg. when in vscode i hovered and clicked on go to definition it went to the location. curious how vscode knows this information.
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4.I was interested to debug unit tests individually and managed to do this by following https://github.com/microsoft/vscode-cmake-tools/blob/main/docs/debug-launch.md#debugging-tests
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