Lesson 19 of 20Practical Modern C++25 min

Debugging and Testing in Visual Studio

Debugging helps you understand why a program behaves differently from what you expected. Testing checks whether important inputs produce the correct results.

A Practical Debugging Workflow

Reproduce the problem with a small, clear input.
Set a breakpoint before the suspected line.
Start debugging and inspect variable values.
Step over one statement at a time.
Correct the cause, rebuild, and repeat the test.

Useful Visual Studio Tools

Tool	Use
Breakpoint	Pauses execution at a selected line.
Step Over	Runs the current line without entering called functions.
Step Into	Moves into a called function.
Locals / Autos	Shows values currently in scope.
Watch	Tracks expressions or variables you select.
Call Stack	Shows the chain of function calls.

Assertions

Simple assertion

#include <cassert>

int calculateDiscount(int percentage)
{
    assert(percentage >= 0 && percentage <= 100);
    return percentage;
}

Small Test Cases

Testing a function

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

int main()
{
    assert(add(2, 3) == 5);
    assert(add(-1, 1) == 0);
    assert(add(0, 0) == 0);
}

Testing habit

Include normal, boundary, and invalid inputs. For a mark, useful boundaries include 0, 50, and 100.

Lesson Summary

Use breakpoints, stepping, inspection, assertions, and small test cases.