Error Guessing in Practice

1. Introduction

The goal of this tutorial is to introduce you to the concept of Error Guessing, a technique used in software testing. You will learn how to employ Error Guessing in your daily programming and debugging tasks to identify potential errors and resolve them.

By the end of the tutorial, you will have a clear understanding of the Error Guessing technique and how to apply it in real-world scenarios.

Prerequisites:
- Basic programming knowledge is required.
- Familiarity with software testing concepts will be helpful but is not necessary.

2. Step-by-Step Guide

Error Guessing is a testing technique where the tester anticipates the occurrence of errors in the software application. It is based on the tester's intuition, experience, and knowledge about the system.

Concept Explanation

The idea behind Error Guessing is simple: leverage your experience and intuition to guess where errors might occur in your application.

This approach is less systematic than other testing methods, but it can be surprisingly effective. In many cases, experienced testers will be able to 'guess' where errors are likely to occur based on patterns they've seen in the past.

Examples

For instance, let's say you're testing a form that accepts user input. Based on your experience, you might guess that errors could occur when:

• The user enters a string where a number is expected.
• The user enters a number that is outside the valid range.
• The input fields are left empty.

Best Practices and Tips

• Use your experience: If you've seen a particular type of error occur frequently in similar situations, it's worth checking for it here.
• Think like a user: Try to imagine how a user might misuse your application, and test for those scenarios.
• Combine with other methods: Error Guessing is most effective when used in conjunction with more systematic testing methods.

3. Code Examples

Code Snippet: Testing a User Input Field

# This is a simple function to test user input
def test_input(input):
    # We guess that errors could occur if the input is not a number,
    # So we test for that
    try:
        value = int(input)
    except ValueError:
        return "Error: Input must be a number"

    # We also guess that errors could occur if the input is outside the valid range,
    # So we test for that too
    if value < 0 or value > 100:
        return "Error: Input must be between 0 and 100"

    # If there are no errors, we return a success message
    return "Input is valid"

In the above code:

• The function test_input accepts an input argument.
• We first try to convert the input to an integer. If this fails, it means the input is not a number, and we return an error message.
• Next, we check if the number is within the range 0-100. If it's not, we return another error message.
• If none of these checks fail, it means the input is valid, and we return a success message.

Expected Output

If we call test_input with various inputs, we should get the following results:

print(test_input("abc"))  # Output: "Error: Input must be a number"
print(test_input("150"))  # Output: "Error: Input must be between 0 and 100"
print(test_input("50"))   # Output: "Input is valid"

4. Summary

In this tutorial, we've learned about Error Guessing, a testing technique where the tester makes educated guesses about where errors might occur in a software application. We've seen how to apply this technique in practice, and looked at a code example that demonstrates this approach.

To continue learning about software testing, you might want to look into systematic testing methods, such as boundary value analysis and equivalence partitioning. These methods can complement Error Guessing and help you create a comprehensive test suite for your applications.

5. Practice Exercises

1. Write a function that tests user input for a registration form. The form requires a username (a string of 3-20 alphanumeric characters), an email address, and a password (a string of 8-30 characters, with at least one number and one special character). Use Error Guessing to anticipate potential errors.

2. Write a function that tests user input for a calculator app. The app should accept two numbers and an operator (+, -, *, /). Use Error Guessing to anticipate potential errors.

Remember, the key to Error Guessing is to leverage your experience and intuition. Try to think about how users might misuse the application, and test for those scenarios.

Happy testing!