Error Guessing is a test design technique used to anticipate defects, failures, and potential issues in software based on a tester’s experience and knowledge. This technique relies on the tester’s intuition, past experience with the application, and an understanding of common mistakes made by developers.

Key Aspects of Error Guessing

A tester uses Error Guessing by considering:

• How has the application behaved in previous versions or releases?
• Common types of errors developers tend to make.
• Failures observed in similar applications or projects.

Errors, defects, and failures can be related to various factors, including:

1. Input Errors: Incorrect input is not accepted, and parameters are missing or incorrect.
2. Output Errors: Incorrect format, wrong results displayed.
3. Logical Errors: Missing cases, incorrect operators used in conditions.
4. Computation Errors: Incorrect operand usage, faulty calculations.
5. Interface Errors: Parameter mismatches, incompatible data types.
6. Data Errors: Incorrect initialization, use of the wrong data type.

Fault Attacks & Systematic Error Guessing

A fault attack is a structured approach to implementing Error Guessing. Testers create or refer to a predefined list of possible defects, failures, and common software issues. Test cases are then designed to identify and expose these defects.

How to Apply Error Guessing Effectively?

Applying Error Guessing effectively requires a methodical approach. Here’s how testers can integrate this technique into their testing process:

1. Leverage Past Experience

Testers should rely on their experience with similar applications and previous projects to predict potential failure points.

2. Analyze Historical Defect Data

Review past bug reports and defect logs to identify patterns and common pitfalls that can be tested.

3. Think Like a Developer

Understanding common coding mistakes that developers make can help testers anticipate where defects might occur.

4. Use Fault Attacks

A fault attack is a structured approach where testers create a list of potential errors and design test cases specifically targeting those defects.

5. Collaborate with Developers

Engaging with developers can provide insights into complex areas of the code that might be prone to errors.

6. Combine with Other Testing Techniques

Error Guessing works best when combined with structured testing techniques like boundary value analysis, equivalence partitioning, and exploratory testing.

Benefits of Error Guessing

• Uncovers Hidden Defects: Helps identify issues that formal testing strategies might overlook.
• Enhances Test Coverage: Targets areas of the application that may not be explicitly covered in test cases.
• Saves Time and Effort: Focuses on high-risk areas, making testing more efficient.
• Improves Software Quality: Reduces the chances of critical defects reaching production.

Limitations of Error Guessing

While Error Guessing is a powerful technique, it does have some limitations:

• Subjective Approach: Relies heavily on the tester’s intuition and experience.
• No Structured Coverage: Lacks formal test design principles, which may lead to gaps in testing.
• Difficult to Replicate: Since it depends on individual expertise, different testers may produce varying results.

Conclusion

Error Guessing is an invaluable technique in software testing, allowing testers to uncover defects through intuition, experience, and targeted testing strategies. While it should not be used as a standalone method, combining it with structured testing techniques can significantly improve the overall quality and reliability of software applications.

By continuously refining their ability to predict errors, testers can become more efficient in identifying and preventing software failures, ensuring a smooth and robust user experience.