How to Debug Code Using ChatGPT

Unlike traditional debugging tools, which can be complex and require specific knowledge of the programming language, ChatGPT is accessible to programmers of all levels and works in any language.

Simply ask ChatGPT specific questions about error messages or unexpected behavior and you’ll get a reply with relevant information that can help you identify and fix the issue.

While every interaction with ChatGPT will be different (it is a chatbot afterall), there are some common steps to follow that will help you engineer prompts that give the best results. This blog post will walk through these steps and share examples.

Step 1: Identify the Problem

The first step in debugging is to identify the problem. This can be the most challenging part of the process, as the problem may not always be obvious. You may have to look for clues, such as error messages or unexpected behavior, to pinpoint the problem. You can ask ChatGPT questions about the error messages or the behavior you are seeing to get a better idea of what is causing the problem.

Step 2: Isolate the Problem

Once we have identified the problem, the next step is to isolate it. This involves finding the exact line or lines of code that are causing the problem. You can ask ChatGPT for help in determining which lines of code are causing the issue.

Step 3: Reproduce the Problem

In order to debug the problem, it's essential to reproduce it consistently. You can ask ChatGPT for guidance on how to reproduce the problem or how to test the code to make sure the problem has been fixed.

Step 4: Understand the Code

To debug code effectively, you need to have a good understanding of how it works. ChatGPT can help you understand the code by answering questions about the code's purpose, structure, and syntax.

Step 5: Use Debugging Tools

There are many tools available for debugging code, such as print statements, breakpoints, and debuggers. ChatGPT can help you learn how to use these tools effectively by providing guidance and answering questions.

Step 6: Test The Fix

Once you’ve identified and fixed the problem, you need to test the code to make sure the problem has been resolved. ChatGPT can help develop test cases and provide guidance for testing the code effectively.

Example One: Debugging NullPointerException

Step 1: Enter the code in the prompt

Enter the code that throws the exception and ask ChatGPT to assess it.

Prompt:

public class Test {

    private static void printLength(String str) {
        System.out.println(str.length());
    }

    public static void main(String []args){

        String myString = null;
        printLength(myString);
    }
}

The above code is not running. Could you tell me what the problem might be?

ChatGPT’s Response:

The code will result in a 'NullPointerException' at runtime when you call the 'printLength' method with 'myString' variable, which is set to null.

The 'NullPointerException' occurs because the 'length()' method is being called on a null object reference. To fix this issue, you can add a null check before calling the 'length()' method.

Here is the updated code:

public class Test {

    private static void printLength(String str) {
        if (str != null) {
            System.out.println(str.length());
        } else {
            System.out.println("String is null.");
        }
    }

    public static void main(String[] args) {
        String myString = null;
        printLength(myString);
    }
}

This code will check if 'myString' is null before calling the 'length()' method, and if it is null, it will print a message to the console.

Step 2: Ask ChatGPT for some test cases

To test that the updated program is correct and runs properly, you can prompt ChatGPT to give some test cases.

Prompt:

Could you tell me some test cases to test the above code?

ChatGPT’s Response:

Certainly! Here are some test cases you can use to test the 'printLength' method:

1. Test with a non-null string:

String myString = "Hello";
printLength(myString);
//Expected Output: 5

2. Test with a null string:

String myString = null;
printLength(myString);
//Expected Output: String is null

3. Test with an empty string:

String myString = "";
printLength(myString);
//Expected Output: 0

4. Test with a string containing whitespace characters:

String myString = "   ";
printLength(myString);
//Expected Output: 3

5. Test with a string containing special characters:

String myString = "Hello, World!";
printLength(myString);
//Expected Output: 13

Example Two: Logical Error

Step 1: Enter the code in the prompt

Enter the code below containing a logical error and ask ChatGPT to check for reasons why the error is occurring.

Prompt:

public class Test {
    public static void main(String[] args)
    {
        int num = 1234;
        int reversednum = 0;
        int remainder;

        while (num != 0) {
            remainder = num / 10;
            reversednum = reversednum * 10 + remainder;
            num /= 10;
        }
        System.out.println("The reversed number is " + reversednum);
    }
}

Why is my code for reversing a number giving a wrong output?

ChatGPT’s Response:

Your code to reverse a number is giving wrong output because you are using integer division instead of modulo operator to get the remainder of the number.

In the 'while' loop, you are using integer division to calculate the remainder:

remainder = num / 10;

This should actually be the modulo operator %:

remainder = num % 10;

The modulo operator returns the remainder of the division, which is what you need to get the last digit of the number. Using integer division will give you the quotient, which is not what you want.

Here's the corrected code:

public class Test {
    public static void main(String[] args)
    {
        int num = 1234;
        int reversednum = 0;
        int remainder;

        while (num != 0) {
            remainder = num % 10;
            reversednum = reversednum * 10 + remainder;
            num /= 10;
        }
        System.out.println("The reversed number is " + reversednum);
    }
}

With this correction, the code should work correctly for all input numbers.

Step 2: Ask ChatGPT for some test cases

This step helps testing the above code.

Prompt:

Could you give me some test cases to test the above code?

ChatGPT’s Response:

Sure, here are some test cases to test your code:

1. Input: 1234, Output: 4321
2. Input: 987654321, Output: 123456789
3. Input: 1001, Output: 1001
4. Input: 0, Output: 0
5. Input: 123, Output: 321

You can try these inputs and verify that the output is correct.

Example Three: Python Code with TypeError

Enter Python code that throws a TypeError during concatenation in the prompt and ask for the reason the code is throwing an error.

Prompt:

mystr = "IronMan"
num = 4
print(mystr + num + mystr)

Why is my code throwing TypeError?

ChatGPT’s Response:

Your code is throwing a 'TypeError' because you are trying to concatenate a string (str) with an integer (num) using the + operator, which is not supported in Python.

In Python, you can only concatenate strings with other strings using the + operator. If you want to concatenate a string with an integer, you need to convert the integer to a string first using the 'str()' function.

Here's the corrected code:

mystr = "IronMan"
num = 4
print(mystr + str(num) + mystr)

In this code, 'str(num)' converts the integer num to a string, which can then be concatenated with the other strings using the + operator. The output of this code will be:

IronMan4IronMan

Note that the integer 4 is now converted to a string and concatenated between the two instances of the string 'IronMan'.

As you can see, ChatGPT is a valuable debugging tool. Fire it up next time you encounter a bug to help overcome coding challenges.

Remember to set up error monitoring to resolve unexpected issues

No matter how smooth your code runs during development and testing, once your code is in production and users test it in unexpected ways or APIs change, it's common for new errors to appear. That’s where an error monitoring tool like Rollbar comes in. Get complete visibility, in real-time, so you can respond to errors right away — before your users notice. Try it today!