Cpp2_9.html

<article>
    <h1>C++ II: Page 9 - Testing: Unit Testing</h1>

    <section>
        <h2>The Quality Assurance Cycle</h2>
        <p>Unit testing is mandatory in professional C++ development. It ensures your code behaves as expected and protects against regressions when you refactor or add new features.</p>
        
        <h3>The Code implementation</h3>
        <pre><code class="language-cpp">
        /*
         * File: test_example.cpp
         * Demonstration of robust unit testing using GoogleTest structure
         */
        #include &lt;iostream&gt;
        #include &lt;cassert&gt;
        #include &lt;string&gt;
        #include &lt;vector&gt;

        using namespace std;

        // Function to test
        int Add(int a, int b) {
            return a + b;
        }

        // A simple test runner (Manual)
        void runTest(bool condition, const string& testName) {
            if (condition) {
                cout << "[PASS] " << testName << endl;
            } else {
                cout << "[FAIL] " << testName << endl;
            }
        }

        int main() {
            cout << "--- Running Tests ---" << endl;

            // Test Case 1: Positive Numbers
            runTest(Add(2, 3) == 5, "Add_PositiveNumbers");

            // Test Case 2: Negative Numbers
            runTest(Add(-1, -1) == -2, "Add_NegativeNumbers");

            // Test Case 3: Zero
            runTest(Add(0, 5) == 5, "Add_Zero");

            // In a professional environment, use Catch2 or GoogleTest:
            /*
            TEST_CASE("Addition works", "[math]") {
                REQUIRE(Add(2, 3) == 5);
                REQUIRE(Add(-1, -1) == -2);
            }

            // GoogleTest example:
            TEST(AddTest, HandlesPositive) {
                EXPECT_EQ(Add(2, 3), 5);
            }
            */

            return 0;
        }

        /*
         * Testing Nuances:
         * 1. Unit tests: Verify the smallest piece of logic in isolation.
         * 2. Integration tests: Verify interaction between modules (e.g., DB connection).
         * 3. Assertions (cassert): Simple runtime checks; use for debugging.
         * 4. Test frameworks (GTest, Catch2): Provide detailed reports, 
         *    test fixtures, and sophisticated assertions.
         * 5. TDD (Test Driven Development): Write the test first, then the code.
         * 6. Coverage tools: Tools like gcov/lcov ensure your tests cover 
         *    the majority of your codebase.
         * 7. Mocking: Use libraries like GoogleMock to simulate dependencies 
         *    (e.g., database, network) to test in isolation.
         */
                </code></pre>
        <div class="interactive-sim">
            <h3>Test Simulator</h3>
            <button class="sim-button" onclick="
                const out = document.getElementById('sim-output-cpp2_9');
                out.innerHTML = 'Running tests...<br>';
                setTimeout(() => out.innerHTML += '>> [PASS] Add_PositiveNumbers<br>>> [PASS] Add_Zero', 800);
            ">Run Simulation</button>
            <div id="sim-output-cpp2_9" class="sim-output"></div>
        </div>
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