A Strategy for Debugging

Vaibhav • September 11, 2025

Debugging isn’t just a skill-it’s a mindset. While the previous article introduced the idea of debugging and how to spot errors, this one focuses on building a repeatable, reliable strategy for solving problems in your code. Whether you’re dealing with a program that crashes, prints the wrong result, or behaves unpredictably, having a structured approach can save hours of frustration.

In this article, we’ll walk through a practical debugging strategy that works even with the limited tools and concepts we’ve covered so far-int, string, decimal, basic input/output, and simple program structure. No methods, no classes, no advanced tools-just logic, observation, and a bit of patience.

Start with a Clear Mental Model

Before you even run your program, take a moment to think: what is this code supposed to do? What should the output look like? What values should each variable hold at different points?

This mental model becomes your reference point. If the program behaves differently than expected, you’ll know something’s off. Debugging starts with knowing what “correct” looks like.

int price = 100;
int tax = 18;
int total = price + tax;
Console.WriteLine("Total price is: " + price);

If your mental model says the output should be Total price is: 118, but the program prints 100, you immediately know where to look. The variable total was calculated, but never used in the output.

Reproduce the Problem Consistently

A bug that happens once and never again is hard to fix. Your first goal is to make the problem happen every time. This might mean using the same input, clicking the same button, or running the same steps in the same order.

If the bug only appears with certain inputs, that’s a clue. Try different values and observe the behavior.

Console.WriteLine("Enter your age:");
string input = Console.ReadLine();
int age = int.Parse(input);
Console.WriteLine("Next year, you will be " + (age + 1));

This works fine if the user types 25. But if they type twenty-five, the program crashes. That’s a reproducible bug. You now have a test case you can use to investigate further.

Use Print Statements to Trace Execution

One of the most powerful debugging tools is already in your toolbox: Console.WriteLine. By printing out variable values at different points in your program, you can see what the computer sees.

int quantity = 3;
decimal price = 9.99m;
decimal total = quantity + price;
Console.WriteLine("Quantity: " + quantity);
Console.WriteLine("Price: " + price);
Console.WriteLine("Total: " + total);

This prints:

Quantity: 3
Price: 9.99
Total: 12.99

That’s not right. You meant to multiply, not add. The print statements helped you catch the mistake.

Check Your Assumptions

Bugs often come from incorrect assumptions. You assume a variable has a certain value, or that a line of code will behave a certain way-but it doesn’t.

The best way to challenge your assumptions is to test them. Print the variable. Run the code. See what actually happens.

int a = 10;
int b = 3;
int average = a + b / 2;
Console.WriteLine("Average: " + average);

You might assume this calculates the average of a and b. But it doesn’t. Division happens before addition, so b / 2 is 1, and the result is 11. The fix is to use parentheses:

int average = (a + b) / 2;

Now the output is correct: 6.

Isolate the Problem

If your program is large, don’t try to debug the whole thing at once. Instead, isolate the part that’s causing trouble. Comment out unrelated code. Focus on the smallest section that still shows the bug.

This makes it easier to reason about what’s happening-and reduces the number of things that could be going wrong.

// Original program
int a = 5;
int b = 0;
int result = a / b;
Console.WriteLine("Result: " + result);

This crashes with a divide-by-zero error. To isolate the problem, you might comment out the division:

Console.WriteLine("a: " + a);
Console.WriteLine("b: " + b);
// Console.WriteLine("Result: " + (a / b));

Now the program runs, and you can see that b is zero. That’s your problem.

Change One Thing at a Time

When you’re trying to fix a bug, don’t change five things at once. Change one thing, run the program, and see what happens. If the bug goes away, you know what fixed it. If it doesn’t, you haven’t made things worse.

This disciplined approach helps you learn from each change-and prevents you from introducing new bugs while trying to fix old ones.

Use Sample Inputs and Outputs

If your program takes input, create a list of sample inputs and the expected outputs. Then run your program with each input and compare the actual output to the expected one.

This helps you catch edge cases-inputs that behave differently than the norm.

// Input: 10, 5 → Expected output: 15
// Input: 0, 0 → Expected output: 0
// Input: -3, 3 → Expected output: 0

If your program fails on one of these cases, you’ve found a bug.

Keep a Debugging Log

As you debug, write down what you tried, what you observed, and what you concluded. This helps you stay organized and prevents you from repeating the same failed fix over and over.

It also helps you learn. Over time, you’ll start to see patterns in the kinds of bugs you make-and how to fix them faster.

Ask “What Changed?”

If your code was working yesterday and it’s broken today, ask yourself: what changed? Did you add a new line? Modify a variable? Change the input?

Often, the bug is in the most recent change. Start there.

Don’t Panic-Stay Curious

Debugging can be frustrating. But it’s also an opportunity to learn. Every bug you fix teaches you something about how computers work, how C# behaves, and how to think more clearly.

So when you hit a bug, don’t panic. Get curious. Ask questions. Run experiments. And trust the process.

Summary

In this article, we explored a structured strategy for debugging:

• Start with a clear mental model of what your code should do
• Reproduce the problem consistently
• Use print statements to trace execution and inspect variables
• Challenge your assumptions and test them
• Isolate the problem to a small section of code
• Change one thing at a time and observe the result
• Use sample inputs and expected outputs to test your logic
• Keep a debugging log to track your progress
• Ask “what changed?” when things break
• Stay curious and treat debugging as a learning opportunity

With this strategy in hand, you’ll be better equipped to tackle bugs with confidence and clarity. In the next article, we’ll explore specific debugging tactics-practical techniques you can use to find and fix problems even faster.